High-resolution study of FO infrared chemiluminescence

JOURNAL OF MOLECULAR SPECTROSCOPY 129,99- 118(1988)

High-Resolution Study of FO Infrared Chemiluminescence PHILIP D. HAMMER,’ AMITABHA SINHA,~ JAMES B. BURKHOLDER, AND CARLETON J. HOWARD NOAAAeronomy Laboratory, R/E/ALZ. 325 Broadway, Boulder. Colorado 80303. and Department of Chemistry and Biochemistry and CIRES, University of Colorado, Boulder, Colorado 80302

Vibrationallyexcited FO radicalsgeneratedby the reactionF + O3 + FO* + O2 have been observedin emission for levels up to u’= 9 in the groundelectronicstate.An infrared spectrum for Au = 1 quantum transitions has been recorded at a nominal resolution of 0.008 cm-’ (125 cm path difference) using a high-resolution Fourier transform spectrometer. Transitions for Au = 2 and 3 up to 9-6 were also observed at lower resolution but were not used in the analysis. An analysis of the X211u2and X2113,2Au = 1 transitions up to u’ = 8 has yielded new information about the vibrational state dependencies of the molecular parameters. Transition intensities and instrumental lineshapes have also been investigated. 0 1988Academic press. hc. INTRODUCTION

As described in a previous paper (I) high-resolution spectra of the FO radical have been observed only recently. Earlier observations of FO were made at low resolution using Raman (2) and infrared (3) detection with low-temperature matrix isolation, and photoelectron (4) and mass (5-7) spectroscopy. The initial high-resolution studies of gas phase FO were done using IR laser magnetic resonance (8) and diode laser spectroscopy with Zeeman modulation (9). Although these techniques have high detection sensitivity, they are limited in their range of spectral coverage and cannot be used to observe the essentially diamagnetic 211i/2 transitions, nor higher J-value 211s,2transitions. More recently, high-resolution absorption spectra of FO were obtained in our laboratory using a Fourier transform spectrometer (ITS) coupled to a multireflection absorption cell (1). Both the 2111,2and the 2113,2 components of the 1-O and 2-O electronic ground state transitions were observed to relatively high J. This study provided new information such as A-doubling parameters as well as improvement of centrifugal distortion parameters which are more accurately determinable from high J transitions. The inherently lower sensitivity of the ITS technique relative to laser modulation methods was overcome by synthesizing FO in high concentrations and using a long absorption path. Fast flow conditions were maintained to reduce the radical residence time within the absorption cell. The detection of free radicals by infrared emission has several potential advantages over the absorption method described above. The volume of the emitting region can ’ Present address: NASA Ames, M/S 245-6, Moffett Field, CA 94035. 2 Present address: Department of Chemistry, University of Wisconsin, Madison, WI 53706. 99

0022-2852/88 $3.00 Copyright 0 1988 by Academrc Press, Inc. All rights of reproduction in any form reserved.

100

HAMMER

ET AL.

be made quite small permitting much shorter residence times within the field of view of the spectrometer. In principle this allows the observation of transitions due to shorter lived species while minimizing interferences due to more stable species. With the elimination of the absorption continuum source and the potential of reducing black body background radiation with appropriately placed cold plates and apertures it is possible to reduce detector noise and other interferences such as &talon effects within windows and filters. Emission studies also have disadvantages which must be overcome such as the reduced sensitivity due to smaller effective column densities of the radical source, the difficulty in interpreting intensity measurements, the loss of emission signal due to excited state quenching, and the difficulty in controlling the radical synthesis chemistry. This paper presents a spectroscopic analysis of the FO radical in light of these instrumental considerations. Transition intensity and instrumental lineshape considerations are also of interest in this work, particularly from an instrumental standpoint. Although the experimental conditions precluded an extensive study in this case, other motivations for obtaining accurate intensity measurements would be to determine transition strengths (i.e., application of the Herman-Wallace effect (10)) and dynamical information about the formation of a molecule (i.e., nascent vibrational populations). Such information is scarce for unstable free radicals. FO plays a minor role in atmospheric chemistry (II). Most free fluorine in the atmosphere is converted to HF which provides a very stable repository, unlike the analogous Cl and Br systems which are known to have relatively long chain reaction processes in the upper atmosphere. EXPERIMENTAL

DETAILS

An overview of the experimental apparatus is shown in Fig. 1. The high-resolution Fourier transform spectrometer (FIS) manufactured by Bomem is described in detail elsewhere (12). The beam splitters used depended on the spectral range desired: KC1 for E -K 1400 cm-’ and CaF2 for i > 1400 cm-‘. A dry ice cooled aperture placed at the first image of the entrance aperture served as the limiting field stop of the spectrometer. This significantly reduced black body radiation incident on the detector from the surroundings, including emission from the entrance aperture iris. The latter could cause difficulties in interpreting emission intensities as will be discussed later. Aperture sizes were chosen according to spectral range and resolution requirements. A typical cold exit aperture size was 2.3 mm for the Av = 1 spectrum analyzed in this work. This corresponded to approximately 50% reduction in fringe contrast at a 125cm path difference for a monochromatic source with F = 1100 cm-’ due to the finite aperture size effect. The detectors used were a liquid He cooled Cu:Ge photoconductor for E < 1900 cm-’ and an InSb photodiode for F > 1850 cm-‘. The dewar for the Cu: Ge was equipped with a wedged KRS-5 window, a liquid N2 cooled filter wheel, and an exchangeable liquid He cooled filter and mask just in front of the detector crystal. For this experiment the latter filter was a BaF2 disk which effectively filters radiation with Z < 700 cm-‘. This eliminated problems with long wavelength transmission of the various unblocked interference filters used in the filter wheel. The filters used were a 880-I 350 cm-’ band pass, a 1160-1400 cm-’ band pass, and a sapphire substrate

101

IR SPECTRUM OF FO High Precision

hemiluminescence

Dewar window FIG. 1. Fourier transform

spectrometer.

Overview

of

Cold mask

experimental apparatus with Cu:Ge

detector.

for 5 > 1350 cm-‘. The aperture in the mask was chosen to roughly match the image size (X 1.3 mm) of the dry ice cooled aperture described above. The mask was located about 2 mm in front of the 2-mm square detector crystal face to avoid undesirable effects which arise from failure to fully illuminate the crystal. The interior of the FE, including the box containing the source collimating mirror, was evacuated to a pressure < 10 mTorr. Figure 2 shows the emission cell. A rear mirror with a radius of curvature coincident with the object plane (center of emission volume) was aligned (though not exactly to avoid interference effects) so as to superimpose the FE entrance aperture on its image. This increased the collection of fluorescence radiation from the cell. The KBr front window was positioned close to the KBr window of the FTS source compartment to minimize the required gas purging path. The cell was equipped with two microwave discharge cavities for producing atomic fluorine. The method of FO radical production was the same as that used for the absorption measurements (I). The essential chemistry is described below: F2 + 2F F + 0s + FO* (U G u,,)

(discharge) + 0~

(2)

FO+FO+2F+02 FO* --f FO + hv

(1)

(3) (IR emission).

(4)

102

HAMMER ET AL.

r F2’He

FIG. 2. Chemiluminescence cm from the window.

reactor. The inner diameter of the main interior is 4 cm and the mirror is 14

The rate constants for (2) and (3) are large for bimolecular reactions, 1.3 X 10-l ’ cm3 molecule-’ set-’ (6) and 1.5 X 10-l ’ cm3 molecule-’ set-’ (7), respectively. In this mechanism, the total FO radical concentration is limited by the initial F concentration, since there is no significant loss of radicals in the presence of excess ozone. The exothermicity of reaction (2) (13), 113 kJ mole-‘, permits population of vibrational levels of FO up to u,,, = 10. This may be compared to the dissociation energy of FO which is estimated to be 220 kJ mole-‘. The reduction of the intensity data requires some discussion. The accuracy of the intensity transformation described under Results and Analysis depends on several instrumental considerations. For instance, the phase characterization of the interferogram is dependent on the radial distribution of radiation sources with respect to the center of the entrance aperture (14). If the spatial illumination of the limiting field aperture is not identical for the various sources of radiation being detected, including that used to determine the Forman phase (15), distortion of the spectra may result. This effect is particularly pronounced if emission from the iris comprising the entrance aperture reaches the detector. Although the latter problem was eliminated with a cooled exit aperture as described above, small but significant problems with the phase characterization still persisted in our results. The primary symptom was a slight asymmetry of the emission lines which is evident in the spectra described under Results and Analysis. The radiation source for the Forman phase was an electrically heated (-200°C) graphite cylinder placed inside the emission cell only for phase characterizations. Although phase characterization difficulties may stem from a variety of causes, the evidence suggests the spatial distribution problem described above. This problem could also result in a distorted continuum spectrum, contributing to systematic errors in interpreting emission intensities. It will be noted that the fit of the transition intensities described under Part B of Results and Analysis reveals small systematic deviations. A solution to this problem might be to independently ensure that the entrance aperture

103

IR SPECTRUM OF FO

is uniformly illuminated for all sources in question, or to independently determine the instrumental transmission and phase function for each source. Typical experimental conditions were as follows. The total pressure in the emission cell was 0.6 Torr, 90% of which was the He carrier gas. The ozone concentration was 2 X 1015 molecule cm-3. The initial F concentration was estimated to be 5 X lOI molecule cme3 assuming that about 30% of the Fz was dissociated in the discharge. This yield was estimated based on previous experience in our laboratory using mixtures of s5% F2 in He flowing through a discharge at a rate of 2 STP cm3 set-’ (STP = 1 atm, 273 K). The total input flow rate was 8 STP cm3 set-‘. The gas residence time within the cell was calculated to be 17 msec. The residence time within the spectrometer field of view was approximately 5 msec. Although not directly measured the interior temperature was estimated to be about 330 K based on fits of rotational band intensities (see discussion). RESULTS AND ANALYSIS

Infrared emission from the FO radical was observed for the electronic ground state vibrational transitions Av = 1 (880-1090 cm-‘), Av = 2 (1730-2090 cm-‘), and Av = 3 (2650-3000 cm-‘). Transitions within the *II,,2 and *II3/2spin states were observed for Av = 1 and 2, but only *II3,2 was detectable for Av = 3. Only Av = 1 spectra were used in the analysis since the other bands were taken at lower resolution (>0.03 cm-‘) and had comparatively worse signal/noise. However, the identification of observed Av > 1 transitions was verified by comparison with line positions calculated from the constants obtained from the analysis of the Av = 1 system. The Av = 3 spectrum had prominent R-branch heads and there was clear evidence for the 9-6 band, although resolution of the individual rotational lines was poor. A survey of the fundamental vibrational spectrum is shown in Fig. 3. Roughly 4000 FO Emission a-7 I

7-6 I

900

6-5 I

5-4 I

925

950

4-3 I

975 V

3-2 I

2-1 I

lclO0

1-o I

Id25

Id50

lci75

(cm-‘)

FIG 3. Survey of FO Au = 1 emission spectrum. The markers show the location of the band origins. The intensity scale has been adjusted as described by Eq. (16) but without the black body radiation factor. The cumulative integration time was approximately 3 hr for 128 scans.

104

HAMMER ET AL.

lines could be resolved although only about 1100 were attributable to FO. The remaining transitions belong to a dense band in the region of 1000-1070 cm-’ which appears to be the 23 band of 03 based on comparisons with assigned line lists (16). The failure to observe the 9-8 band was due in part to the long wavelength cutoff of the cooled filter described under Experimental Details. A portion of the spectrum is shown in more detail in Fig. 4. For the most part 211,,2 rotational transitions were resolvable except for the high J R-branch A doublets. 2113,2 A doubling was generally unresolvable as expected. Absolute frequency calibration was achieved by comparison of the 1-O emission band of FO with the corresponding 1-O absorption band (I). The latter was calibrated with respect to transitions of the N20 OO’l-00’0 band near 1250 cm-’ (17). Line positions were determined by locating the zero crossings of the differentiated spectrum. Prior to this a spectral sampling interval of 0.0020 cm-’ was obtained by zero-filling the interferogram from a 125 to a 250-cm maximum path difference. This gave adequate sampling of the FO lineshapes. The observed emission line positions were found to deviate systematically from the absorption lines by -0.0012 cm-‘, and a constant correction term of +0.0012 cm-’ was added to all the emission lines prior to analysis.

A. Line Position Analysis For consistency with the analysis of the absorption results (I) the analysis was done using essentially the same Hamiltonian. This is the effective molecular Hamiltonian approach of Brown and co-workers (18). Below are the matrix elements for the rotational energy levels F(J),

I

(a)

6-5

(W

Cc) (d)

:;z

“R

e ’f

5_4 4.3 3.2 2.1

FIG.

312 3/Z 3’2 112 312 112 3/Z

f,e f,e

P Q P P P P P

g&.o., : : : :

944.0

:

, 8.5

: : : 945.0

:

:

: : : 946.0

19.5 I 9.5 2.5 I

:

:

947.0

:

:

:

:

110.5 110.5

Ill.5 9:5 11.51

II 11.5

119.5 1 19.5

I 28.5

112.5 I 1111 c5 4:5’ ‘1.5 10.5,

110.5 I 20.5

II 20.5

cm-’

Ill.5 !

12.5,

:

948. 0‘

nm.5 I 27.5

4. Selected detail of Fig. 3. (a) Vibrational band, (b) spin state, (c) symmetry, (d) branch.

IR SPECTRUM

105

OF FO

(2113,21H12113,2) = $(A + A,,z) + Bz - Dz(z + 1)

(5)

(211,,#!Z1211,,2) = -$(A + An(z + 2)) + B(z + 2) -D(z2+5z+4)+$(J++)[p+2q+pD(z+2)]

(6)

(*rx3,*JH1*rI,,*) = -\rz[B - 2D(z + 1) -t 3(J + $)(q + 3pD)], (7) where z = (J + f )’ - 1. In these expressions, A is the spin-orbit interaction parameter, An is the centrifugal distortion of A, p and q are A-doubling parameters, pi is the centrifugal distortion of p, and B and D are the rotational and centrifugal distortion parameters. The f signs correspond to the f/e A-doubling components which were labeled to agree with the assignments for the Cl0 radical. For the *IIj12 transitions and some high J R-branch *II,,* transitions this splitting was not resolved. In these cases the observed line positions were fitted to the mean of the predicted A doublet. The spin-rotation parameter, y, was set to zero and q was set to a constant consistent with those for the isovalent radicals Cl0 and BrO as described in the FO absorption paper (I). The dependence of the above constants on the vibrational quantum number, u, was expressed in power expansions in v + i : (19)

(8)

spin-orbit: n

(9)

(10)

rotation:

(12)

A doubling: PD=PDe q = qe = 7.0 X 10d5 cm-‘.

(13) (14)

The maximum value of IZfor each summation was chosen such that CY,for n > ~~~~ were statistically insignificant. Similarly, the vibrational energy term was expressed as G(U) = we(v + ;> - w,x,(v + 1)’ + w,y,(v + $)’ + w,z,(v + 4)” + o,u,(v + f)‘. (15) The energy eigenvalues were obtained by diagonalizing the 2 X 2 matrix given by Eqs. (5)-(7) and directly adding the vibrational term. All rotation-vibration transitions were fitted simultaneously to the appropriate differences of the energy eigenvalues. Quantum number assignments for the higher v transitions were based on extrapolations from the known assignments for the 1-O and 2-O transitions. The identification of the transitions was aided by user interactive molecular analysis software (20). The FO absorption data (I) were also included in the final fit.

HAMMER

106

ET AL.

The squares of the residuals comprising the variance, X2, were weighted as follows: 1.0 for the 1-O through 6-5 emission bands, 0.25 for the 7-6 band, 0.2 for the 8-7 band, and 4.0 for the I-O absorption band. The latter spectrum was taken at higher resolution and was superior in signal/noise. Weights were based on the relative values of the inverse squares of the standard residuals derived from fits restricted to individual vibrational bands. The measured transitions and their deviations from the model fit discussed above are listed in Table I. The standard deviation of the residuals was 0.00052 cm-‘. The fitting results for the absorption data are omitted from the table since the residuals are almost the same as in the FO absorption paper. Table II lists the resulting values and standard errors of the Hamiltonian parameters. Table III gives the corresponding parameter values and errors calculated for each vibrational band derived from the variance-covariance matrix of the fit. B. Line Intensities and Instrumental Lineshapes Also shown in Table I are peak intensity values for the transitions. Direct information on the relative scaling of the intensities over the spectral region was not available as for the case of the absorption spectra. However, it was possible to derive a consistent scale over the entire Av = 1 system, since the raw spectral data consisted of emission lines on top of a continuum spectrum. The amplitude of the continuum was roughly the same as the net peak amplitude for the strongest lines. The continuum did not appear to be influenced by the experimental conditions within the chemiluminescence reactor, This was consistent with the assumption that the continuum source was just room temperature black body radiation originating from outside the emission cell. Since the limiting field stop of the spectrometer was the exit aperture, no black body contributions from the entrance iris were present. This could cause complications as described under Experimental Details. The transformation to a meaningful intensity scale I@), which is corrected for instrumental transmission, was achieved as follows:

1

r(s) - 1 B&G).

I(i)

= A _ [ 44

(16)

Here, r(F) is the raw total amplitude of the spectra, c(3) is the raw continuum amplitude only, B3&) is the 300 K black body emission function in intensity units, and A is an arbitrary constant. The corrected peak transition intensities were compared to a simple Hund’s case (a) model of rotational intensity distributions within a vibrational band (21) I(C)

=

CSJG4e-B’J’(J’+1 )hc/kT >

(17)

where B’ is the rotational

constant of the upper vibrational state, C is an arbitrary factor and S, is the Honl-London factor (21): pq = .I

(J’ + WJ’ - Q) J’

(18)

IR SPECTRUM

107

OF FO

TABLE I Observed Transitions of FO for Au = 1 Emission (in cm -I; Obs - Calc in Units of low4 cm-‘) 1-O Band J

R(J)

211 312 o-c

1.5 2.5 3.5 4.5 5.5 6.5 7.5

1038.6198 -26* 1040.6216 -2 1042.5941 0 1044.5388 -6 1046.4581 7 1048.3480 0 1050.2114 1 8.5 1052.0456 -12* 9.5 1053.8547 0 10.5 1055.6349 0 11.5 1057.3874 2 12.5 13.5 1060.8074 -3 14.5 1062.4757 1 15.5 1064.1153 1 16.5 1065.7265 1 17.5 1067.3093 2 18.5 1068.8630 0 19.5 1070.3884 3 20.5 1071.8846 3 21.5 1073.3516 1 22.5 1074.7899 3 23.5 1076.1984 1 24.5 1077.5780 3 25.5 1078.9280 4 26.5 1080.2479 1 27.5 1081.5386 4 28.5 1082.7989 1 29.5 1084.0293 -1 30.5 1085.2295 -3 31.5 1086.3991 -7 32.5 1087.5408 12*

1-O Band J

1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5 20.5 21.5 22.5 23.5 24.5 26.5 27.5

se(J) 1037.5827 1039.5964 1041.5898 1043.5526 1045.4896 1047.3979 1049.2781 1051.1306 1052.9547 1054.7502 1056.5174 1058.2563 1059.9657 1063.2990 1064.9219 1066.5173 1068.0814 1069.6151 1071.1210 1072.5962

I

P(J)

o-c

I

21 24 1028.2231 2 9 36 1026.0631 -2 26 46 1023.8774 0 36 60 1021.6650 -1 46 56 1019.4268 1 51 60 _ _ 90 1014.8718 1 64 63 1012.5552 -1 68 61 1010.2130 -1 64 64 1007.8455 3t 77 - 1005.4518 1 63 62 1003.0327 1 60 54 1000.5aai 0 57 49 998.1183 2 52 47 995.6232 3 55 43 993.1026 0 44 37 990.5571 1 40 34 987.9866 1 35 29 985.3912 2 29 24 982.7653 -53* 48 22 980.1202 -52* 51 17 977.4556 1 19 14 974.7614 3 15 11 972.0418 -2 12 10 969.2982 -3 11 7 966.5305 0 8 5 963.7380 -3 6 6 960.9239 211 6 4 958.0811 1 3 3 3

Q(J) 1033.4560 1033.3895 1033.2961 1033.1751 1033.0282 1032.8547 _ 1032.4269 _ 1031.8924

o-c

I

-1 2 3 -6 -7 -6

21 14 11 7 12 9 .

-11

7 . -13* 3

2n 1/2

o-c

I

50* -6 lat -3 4 3 1 2 3 1 1 5 -1

18 6 30 11 13 20 13 13 13 19 15 14 15

o-c

I

1037.5934 19 _ . 1041.6017 -4 1043.5655 -4 1045.5016 -3 1047.4092 -a 1049.2904 3 1051.1419 -1 1052.9656 -1 1054.7621 11 1056.5275 -4 1058.2658 -3 1059.9764 7 - - 1061.6544 -19* 0 12 1063.3088 7 -1 10 1064.9313 5 14 10 1066.5244 1 10 9 1068.0907 22% -5 7 1069.6225 -7 -1 a 1071.1284 0 -9 5 1072.6036 -3 1074.0463 -2 5 1075.4625 1 4 1076.8491 7 3 1079.5279 -18 2 1080.8232 -16 3

4 10 11 11 13 15 15 14 19 13 13 12 32 11 9 9 12 8 6 5

a$J)

P&J)

1027.0714 1024.8893 1022.6845 1020.4447 1018.1819 1015.8923 1013.5786 1011.2354 1008.8680 1006.4740 lOo4.0541 1001.6080 999.1378 996.6407 994.1173 991.5697 988.9952 986.3966 983.7730 981.1237 978.4492 975.7529 973.0257

o-c

I

-1 2 47* 7 4 -3 l4* -2 2 0 -2 -6 6 6 -1 3 -6 -4 -1 -4 -a 18 -16

4 7 7 13 12 14 24 14 14 14 19 14 13 12 13 12 11 a a 6 4 4 3

P,(J)

o-c

T

1027.0893 2a* 33 1024.9055 11 10 1022.6948 -6 R 1020.4599 1 II 1018.1978 3 10 1013.5945 1011.2527 1008.8849 1006.4907 1004.0713 1001.6261 999.1562 996.6581 994.1350 991.5867 989.0138 986.4148 983.7909 981.1423 978.4690 975.7699 973.0460

a+ 5 2 -3 0 2 16* 4 -1 -4 1 -2 -2 1 7 h 4

22 14 I4 I5 14 14 66 14 10 l?

'1 x 6 6 4 I, 2

Note: Intensities are normalized for the entire Au = I system as explained in the text. Transitions omitted from the Hamiltonian fit due to spectral interferences are designated by (*). These, together with those designated by (t) were also omitted from the rotational intensity profile fits.

108

HAMMER

ET AL.

TABLE I-Continued 2-l Band .J 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5 20.5 21.5 22.5 23.5 24.5 25.5 26.5 27.5 28.5 29.5 30.5 31.5 32.5 33.5 34.5

R(J)

2n 312 o-c

1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5 20.5 21.5 22.5 23.5 24.5 25.5 26.5 27.5 28.5

P(J)

1018.1156 -2l* 11 1020.0884 -6 25 1022.0326 -1 35 1023.9487 -3 43 1025.8375 0 52 1027.6981 -2 57 1029.5312 Ot 81 1031.3360 0 66 1033.1127 -1 64 1034.8598 -15+ 76 1036.5815 -1 71 1038.2734 0 64 1039.9363 -2 55 1041.5709 -2 54 1043.1767 -1 51 1044.7536 -1 46 1046.3013 -1 42 X347.8194 -6 33 _ _ 1050.7694 0 27 1052.1994 -5 23 1053.6009 3 23 1054.9694 -22* 54 1056.3125 -2 14 1057.6239 1 12 1058.9040 -6 8 1060.1559 6 7 1061.3745 -9 5 1062.5670 20t 6 1063.7252 13. 4 1064.8494 -26* 3 1067.0173 23

Re(J)

1007.8559 1005.7185 1003.5578 1001.3705 999.1562 996.9160 994.6491 992.3559 990.0364 987.6907 985.3192 982.9216 980.4980 978.0488 975.5737 973.0731 970.5469 967.9947 965.4183 962.8160 960.1881 957.5358 954.8578 952.1550 949.4271 946.6741 943.8964 941.0939 938.2681 935.4151 932.5370 929.6390 2 926.7150

2n

2-l Bend J

I

o-c

I

o-c

I

3ot 13 -3 25 -4 38 -1 52 -5t 66 -2 59 -2 64 -2 66 -2 67 -3 67 -2 64 -2 65 -3 60 -2 56 -3 51 -3 47 -3 40 -at 50 -2 31 -1 26 -3 23 1 19 0 16 1 13 -1 11 -4 9 -5 7 -8 5 3 5 -12 3 -33* 1 -9 2 0 2

o-c

Q(J) 1013.0187 1012.9510 1012.8566 _ 1012.5832 1012.4099

I

-5 25 -3 14 2 11 . . -2l* 5 10 5

l/2 Rf(J)

o-c

I

4 1017.0503 -9 5 1017.0389 11 6 1019.0278 -6 13 1019.O419 3 8 1021.0033 -6 10 1020.9906 -5 1022.9250 -6 10 1022.9364 -18 12 3 14 1024.8437 -5 14 1024.8323 1026.7097 -3 13 1026.7212 -6 13 1028.5615 19* 11 1028.5707 -4 16 1030.3805 0 15 1030.3914 -4 14 _ . - 1032.1838 1 16 1033.9360 -31 48 1033.9465 -3 16 3 16 1035.6807 -3 15 1035.6713 1037.3764 -1 13 1037.3862 0 14 2 13 1039.0623 2 12 1039.0530 lo40.7oo5 6* 21 1040.7097 9 10 1042.3179 4 13 1042.3269 8 12 3 11 1043.9136 -1 9 1043.9059 a 1045.4635 -6 LO 1045.4717 -1 1046.9956 -8 8 1048.4939 -10 6 1049.9596 -38* 7 1051.4016 -1 6 1052.8065 -5* 35 1052.8161 35* 4 1054.1852 5* 6 1054.1928 29* 8 1055.5335 -9 5 1056.8515 8 4 1058.1380 18 3

P&J)

o-c

942.0193

P,(J)

o-c

I

1006.6817 -16* 17 1004.5271 -2 6 1002.3438 -2 9 1000.1335 -1 11 997.8959 -3 13 995.6330 11 11 993.3401 -6 13 13 991.0228 -1 14 -6 16 988.6782 -2 15 986.3070 -5 13 -5 16 983.9099 -3 13 -5 16 981.4867 2 14 -6 13 979.0362 -4 12 -1 12 -4 12 974.0584 -1 11 -1 9 971.5304 -3 9 0 9 8 14 968.9767 -2 8 966.3974 1 4 7 9 _ -6 6 961.1613 -2 -1 6 5 958.5053 1 5 1 6 _ _ - 953.1168 -1 4 12 4 950.3849 1 3 7 2 947.6271 -5 1 19 2 944.8487 34* 2 942.0392 11 2 1* 11

1006.6680 -4* 1004.5111 -10 1002.3275 -11 1000.1181 1 997.8797 -6 _993.3240 -4 988.6611 986.2901 983.8925 981.4686 979.0190 976.5425 974.0407 971.5127 968.9596 966.3796 963.7733 961.1430 958.4869 _ 953.0993 950.3668 947.6106

I

13 7 15 13 12

IR SPECTRUM

109

OF FO

TABLE I-Continued

J

1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5 20.5 21.5 22.5 23.5 24.5 25.5 26.5 27.5 28.5 29.5 30.5 31.5 32.5 33.5 34.5

997.1356 999.0786 1000.9930 1002.8795 lOo4.7338 1006.5678 1008.3695 1010.1427 1011.8872 1013.6027 1015.2901 1016.9482 1018.5770 1020.1769 1021.7471 1023.2882 1024.7998 1027.7332 1029.1552 1030.5472 1031.9084 1033.2433 1034.5410 1035.8096 1037.0500 1038.2579 1039.4374 lo40.5794 1041.6958 1042.7811 1043.8325 1044.8526 1045.8414

o-c

I

-1 4 3 3 3 3 2 3 2 -1 2t 37 1 2 -1 1 2 _ 0 -1 0 -4 32* 0 -16 -6 -14 6 -3w -22 -4 -9 -9 -3

17 28 42 52 61 67 70 74 76 82 94 99 67 62 60 52 48 _ 39 32 29 26 48 17 18 14 8 9 31 7 4 3 4 3

1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5 20.5 21.5 22.5 23.5 24.5 25.5 26.5 27.5 28.5

P(J)

987.0085 984.9005 982.7653 980.6022 978.4126 976.1963 973.9529 971.6827 969.3860 967.0624 964.7125 962.3360 959.9333 957.5041 955.0488 952.5676 950.0600 947.5267 944.9674 942.3824 939.7713 937.1351 934.4730 931.7851 929.0716 926.3336 923.5701 920.7805 917.9659 915.1267 912.2634

o-c

I

9 10 10 3 3 3 3 2 3 2 2 2 2 0 0 1 -1 0 0 0 -2 0 0 -2 -6 -1 3 -2 -5 -2 10

14 33 48 54 61 68 72 74 75 76 74 71 66 62 57 47 47 40 36 32 27 22 19 14 13 9 8 6 5 4 3

o-c

I

996.0284 -9 996.0171 9 6 997.9892 -12 997.9761 -15 13 999.9108 3 12 999.9223 -7 lOO1.8158 lot 22 1001.8253 -16* lOO3.6904 0 14 1003.7020 -2 _ 1005.5374 3 14 1007.3557 8 21 1007.3659 0 1009.1439 3 16 lOO9.1540 -2 1010.9035 4 16 1010.9148 14* 1012.6338 4 16 1012.6432 0 _ 1014.3346 5 17 1016.0055 1 17 1016.0148 4 1017.6472 3 14 1017.6558 3 1019.2593 7 16 1019.2676 8 1020.8406 2 14 1020.8498 16 1022.3920 -1 9 1022.3994 0 1023.9137 2 13 1023.9211 6 1025.4039 -8 9 1025.4107 -5 1026.8653 -1 10 1026.8722 7 1028.2988 6 9 1029.6974 0 12 1031.0637 -19* 10 1032.4063 35* 33 1033.7109 20 6 1034.9841 4 4 1036.2280 9 5

6 15 10 18 13

R,(J)

Q(J) 992.1066 992.0369 991.9412 991.8147 991.6657 991.4864 991.2790 991.0440

o-c

I

4 -2 7 -17* 11 11 8 4

24 19 15 87 10 6 5 4

2, l/2

3-2 Band J

_~

2n 312

3-2 Band

o-c

I

L$(J)

_

15 17 42 20

_

16 14 11 12 10 12 9 7

Pf(J)

o-c

_ -33* -7 981.4980 -5 979.3130 -3 977.1009 3 974.8607 2 972.5930 -1 970.2983 -3 967.9769 -1 965.6285 2 963.2531 3 960.8505 0 958.4215 0 955.9661 3 953.4840 3 950.9752 0 948.4421 18* 945.8800 7 943.2922 19 940.6792 5 938.0397 3 935.3733 -9 932.6838 7 929.9664 0 927.2244 4 924.4561 13 921.6615 -11 985.782; 983.6554

I

P,(J)

o-c

1

7 9 12 13 14 14 16 19 19 16 16 15 16 14 14 11 lb 9 6 5 5 3 3 3 2

985.8007

983.6714 981.5144 979.3287 977.1162 974.8768 972.6092 970.3150 967.9947 965.6450

963.2701 960.8678 958.4388 955.9835 953.5016 950.9929 948.4587 945.8977 943.3106 940.6969 938.0584 935.3891 932.7040 929.9860 927.2442 924.4752 921.6814

0

7

4 6 -1 -2 2 -2 -1 lo* -3 1 0 -2 -1 0 -4 1 1

9 15 11 13 15 14 16 50 29 lh 15 16 Lh 13 12 Y

1 -4

IL 8 6

2 -4o* 19* 4 10 -1 -4

5 3 17 3 3 3 3

110

HAMMER

ET AL.

TABLE I-Continued

2,312

4-3 Band J

1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5 20.5 21.5 22.5 23.5 24.5 25.5 26.5 27.5 28.5 29.5 30.5 31.5 32.5

NJ)

o-c

975.6319 -at 13 5 32 977.5461 979.4306 4 45 981.2865 4 57 983.1135 3 67 984.9118 2 76 2 77 986.6812 1 82 988.4215 1 83 990.1326 991.8147 3 87 993.4668 -1 82 0 80 995.0899 996.6830 -1 76 _ 999.7802 0 65 1001.2837 0 61 1002.7570 -1 54 1004.2001 0 49 1005.6126 -1 40 1006.9944 -3 36 1008.3456 -3 31 1009.6671 7* 43 1010.9557 -1 22 1012.2146 5 18 1013.4411 0 14 1014.6370 4 13 1015.8002 -4 11 1016.9321 -8 12 1018.0322 -lo* 19 1019.1019 5 9 1020.1381 6 4 1021.1419 6 5

1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5 20.5 21.5 22.5 23.5 24.5 25.5 26.5 27.5

R,(J)

P(J)

965.6450 963.5624 961.4528 959.3156 957.1507 954.9585 952.7386 950.4915 948.2171 945.9156 943.5870 941.2314 938.8489 936.4396 934.0034 931.5408 929.0516 926.5357 923.9934 921.4246 918.8297 916.2083 913.5615 910.8875 908.1881 905.4621 902.7121 899.9338 897.1320

o-c

I

11t 2 3 3 3 4 3 2 2 2 2 1 0 0 -1 -1 0 -1 -2 -3 -2 -3 3 -3 -1 -5 10 18 14

29 31 45 57 66 73 77 80 80 81 78 76 70 67 61 56 48 43 38 34 29 25 23 17 12 12 11

o-c

I

Q(J)

o-c

I

970.6739 4 970.6037 6 970.5053 6 970.3784 3 970.2237 3 970.0401 -3 969.8297 4 969.5898 -2 969.0269 0 968.7029 -1

26 17 12 11 8 6 5 4 3 2

4

2n l/2

4-3 Band J

I

o-c

I

974.4685 -1 7 976.4001 1 8 978.3023 1 11 3 12 980.1757 982.0195 2 15 5 18 983.8343 985.6189 2 18 0 19 987.3741 989.0997 1 19 1 19 990.7954 992.4605 -4 21 _ _ _ 995.6998 -18 17 997.2764 0 17 998.8215 9 17 1000.3345 3 16 1001.8158 -ll* 22 1003.2702 1004.6915 1006.0805 1007.4385 1008.7665 1010.0611 1011.3255 1012.5552 _ 1014.9207

R,(J) 974.4798 976.4122 978.3143 980.1868 982.0304 983.8444 985.6292 987.3841

-15 6 -1 7 0 13 -2 14 -2 16 -3 17 0 18 -1 19

990.8051 5 992.4699 1 994.1052 3 995.7105 9 997.2841 1 998.8273 -4

18 18 17 17 13 20

1001.8253 22* 18 -13* 16 -5 11 -7 11 -5 9 13 11 13 10 29* 15 17* 68 _ 20 4

Q(J)

o-c

_ 964.3805 962.2772 960.1456 957.9859 955.7982 953.5824 951.3394 949.0679 946.7694 944.4432 942.0891 939.7081 337.2999 934.8644 932.4015 929.9120 927.3954 924.8523 922.2824 919.6861 917.0656 914.4125 911.7367 909.0306 906.3050

3 2 1 0 0 -3 1 -2 1 2 -1 0 2 2 -1 -1 -1 0 18 5 33* -1 3 -33* -1

I

P,(J)

o-c

I

_ 6 9 10 12 16 15 17 17 17 22 16 16 15 14 13 11 11 10 8 25 6 4 2 4

964.3960 15 962.2917 0 960.1605 -1 958.0012 0 955.8140 1 953.5984 -2 951.3558 3 949.0846 1 946.7861 1 944.4600 1 942.1066 2 939.7254 -1 937.3173 -1 934.8820 0 932.4194 -2 929.9301 -1 927.4134 -5 924.8710 2 922.3007 -3 919.7043 -1 917.0808 -5 914.4310 -7 911.7553 -4 909.0536 2 906.3232 -15 903.5703 4

6 8 10 13 15 1.6 16 17 17 19 16 15 15 14 13 11 11 8 9 7 6 5 5 4 2 2

IR SPECTRUM

OF FO

111

TABLE I-Continued 5-4

J 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5 20.5 21.5 22.5 23.5 24.5 25.5 26.5 27.5 28.5 29.5 30.5 31.5 32.5 33.5 34.5

*II 3/*

Band

R(J) 953.5569 955.4379 957.2942 959.1183 960.9132 962.6788 _ 966.1209 967.7973 969.4437 971.0601 972.6463 974.2022 975.7277 977.2225 978.6865 980.1202 981.5221 982.8933 984.2330 985.5412 986.8179 988.0629 989.2764 990.4572 991.6062 992.7223 993.8066 994.8580 995.8753 996.8607 997.8123 998.7314 999.6174

o-c

I

-9t -2s 1 -1 -1 -1 _ -2 -3 -3 -3 -3 -3 -2 -2 -3 1 -2 0 -1 -2 -2 -2 3 0 2 -1 2 4 -7 -6 -13 -10 -3

10 48 41 47 58 63 _ 70 72 71 70 68 65 61 58 52 51 42 38 33 28 24 22 19 14 12 9 7 7 5 6 4 3 2

1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5 20.5 21.5 22.5 23.5 24.5 25.5 26.5 27.5 28.5

R,(J)

o-c

I

943.7109 -3t 11 941.6560 -1' 28 939.5723 -1 38 937.4606 1 47 935.3205 1 55 933.1523 1 60 928.7318 1 65 926.4797 -1 67 924.1999 -1 67 921.8924 -1 65 919.5573 -1 65 917.1946 -2 60 914.8045 -2 57 912.3871 -2 53 909.9425 -2 48 907.4704 -3 41 904.9712 -4 37 902.4450 -3 33 899.8919 -2 29 897.3118 -2 24 894.7049 1 19 892.0705 -5 19 889.4098 -4 16

Q(J) 948.6704 948.5986 948.4980 948.3685 _ 948.0223 947.8077 947.5626 947.2910 946.9873

o-c

I

0 0 1 -1

22 14 11 7 _ -11 6 0 5 -5 5 13 2 -3 2

*II l/2

5-4 Band J

P(J)

o-c

I

952.3424 -7 5 954.2439 3 9 2 10 956.1147 957.9555 -1 10 959.7657 -9 17 961.5477 -1 14 963.3002 15+ 27 965.0193 0 16 966.7094 -1 16 968.3689 -3 17 969.9974 -6 18 971.5961 -1 15 1 15 973.1635 974.7024 976.2070 977.6805 979.1213 980.5314 981.9099 983.2559 984.5705 985.8523 987.1023 988.3177 989.5032 990.6536 991.7732 992.8577

o-c

I

952.3564 9 954.2556 0 956.1261 0 957.9661 -6 959.7772 -3

5 7 9 12 13

963.3090 4 965.0287 -2 966.7187 1 968.3779 1 970.0063 0 971.6042 2 973.1702 -5 -4 14 -4 17 -1 12 -10 13 -9 12 -5 12 -8 11 -3 11 -3 11 3 9 -12 8 2 5 -6 4 8 5 4 4

13 16 15 15 14 12 13

R,(J)

PfW

o-c

-

_

942.3990

-5 -2 0 -1 -1 -3 -4 -3 -3 -5 -3 -2 _ -1 -2 -1 -2 -3 -2 -2 -3

4 7 9 12 12 13 13 14 15 14 14 14 _ 12 11 10 9 8 6 5 4

940.3231 938.2183 936.0844 933.9219 931.7307 929.5112 927.2634 924.9873 922.6829 920.3507 917.9905 913.1864 910.7425 908.2713 905.7723 903.2458 900.6922 898.1111 895.5028

I

P,(J)

942.4119 940.3357 938.2328 936.1001 933.9375 931.7470 929.5277 927.2802 925.0039 922.7006 920.3680 918.0084 915.6198 913.2040 910.7610 908.2897 905.7909 903.2650 900.7110 898.1300 895.5231

o-c

I

-17 -2o* -3 5 1 3 1 2 -3 4 -1 4 -3 -3 2 0 -1 19 -3 -4 8

5 14 6 11 11 13 lh 16 14 14 14 13 11 13 12 IO 9 7 5 4

HAMMER

112

ET AL.

TABLE I-Continued

Zn3/z

6-5 Band .J

R(J)

o-c

I

P(J)

o-c

I

Q(J)

o-c

I

1 -1 -6 3 -3 -13 -6 0 12 13

13 9 7 5 4 4 3 2 2

o-c

I

1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5

10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5 20.5 21.5 22.5 23.5 24.5 25.5 26.5 27.5 28.5 29.5 30.5 31.5 32.5

J

1.5 2.5 3.5 4.5 5.5 6.5 7.5 a.5 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5 20.5 21.5 22.5 23.5 24.5 25.5 27.5

-11 6 -3 17 0 22 -3 27 -1 32 -3 36 -2 40 -1 42 -2 42 944.8225 946.4320 -1 43 948.0106 -2 41 949.5503 -1 41 0 38 951.0749 4 40 952.5607 954.0143 0 34 12* 48 955.4379 956.0276 1 30 958.1867 2 27 5 24 959.5140 3 21 960.8088 962.0715 4 18 mll* 27 963.3002 4 15 964.4994 965.6644 6 11 6 a 966.7965 967.0956 8 8 -a* 14 960.9596 4a* 18 969.9974 11 5 970.9924 2 3 971.9562 3 972.8883 11 2 2 973.7842

930.8518 932.7040 934.5260 936.3174 938.0792 939.8105 941.5117 943.1824

R,(J)

o-c

929.5816 6 931.4498 0 933.2887 6 935.0963 4 936.8735 5 938.6198 3 940.3357 a 942.0193 -1

I

3 4 6 7 a 8 14 11 945.295; 5 9 946.8858 a lo 948.4421 -la* 16 949.9746 951.4694 952.9322 954.3631 955.7610 957.1285 958.4616 959.7657 961.0302 962.2644 963.4653 964.6330 965.7680 967.9352

926.0393 921.1520 919.1237 917.0656 914.9802 912.8649 910.7207 908.5481 906.3467 904.1168 901.8584 899.5716 897.2566 894.9132 892.5417 890.1425 887.7152 885.2595

Rf(J)

2 0 -a 2 0 -1 0

6 15 25 30 30 34 36

0 0

39

0 0 0 -1 -2 2 4 2t

38 39 37 37 37 34 32 26 31

o-c

I

929.5943 14 3 931.4653 40* 13 933.2989 -3 6 935.1071 5 a 936.8834 1 a 938.6293 1 a _-942.0284 1 a 943.6814 945.3027 3 1 946.6924 -2 940.4507 -3 1 9 -1 10 -3 9 -3 9 -9 9 6 a 3 a 3a* 17 6 7 2 7 -2 6 -3 5 4 5 5 4

9 a a 7

925.9655

925.8618 925.7302 925.5675 925.3750

925.1547 924.9047 924.6257 924.3150

Q(J)

_

_

_

919.7851 917.7360 915.6585 913.5512 911.4130 909.2477 907.0518 904.8266 902.5733 900.2911 897.9796 895.6399 893.2714

-3 -7 1 5 -6 5 2 -4 -2 1 0 2 3

4 4 5 7 6 a 7 7 9 a 9 a 10

P,(J)

919.8003 917.7497 915.6736 913.5615 911.4295 909.2621 907.0682 904.8431 902.5900 900.3080 897.9969 895.6573 893.2891

o-c

I

11 -12 6 -41* 7 -6 7 -1 1 3 2 4 5

2 4 4 23 6 8 1 a 10 7 6 a 8

IR SPECTRUM

113

OF FO

TABLE I-Continued 7-6 Band J

1.5 2.5 3.5 4.5 5.5 6.5 8.5 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5 20.5 21.5 22.5 23.5 24.5 25.5 26.5 27.5 29.5 30.5 32.5

E(J) 907.4528 909.2721 911.0607 912.8187 914.5456 916.2415 919.5397 921.1422 922.7122 924.2511 925.7582 927.2338 928.6764 930.0877 931.4653 932.8122 934.1253 935.4052 936.6525 937.8660 939.0468 940.1940 941.3078 942.3824 943.4325 944.4432 946.3653 947.2695 948.9781

2n o-c

1.5 3.5 4.5 5.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5 20.5 21.5 22.5 23.5 24.5 25.5 26.5 27.5

R,(J)

906.1180 909.7557 911.5299 913.2726 916.6595 918.3069

NJ)

-1 3 1 5 1 a 4 10 3 12 3 15 3 17 7 16 1 16 2 17 2 16 7 14 3 14 9 12 1 13 12 10 12 10 9 9 11 8 6 7 8 5 9 7 13 6 -36* 32 10 3 5* 22 36* 2 5 2 -5 2

o-c

_ _ _. 895.8992 -11 893.8707 10 891.8102 9 _.885.4497 -41 883.2710 -51

I

4 10 9 25 29

2n l/2

7-6 Band J

I

B-7 Band

3/2

o-c

I

Rf(J)

o-c

19 2 906.1265 -11 -10 2 909.7676 3 -1 2 911.5414 12 7 3 913.2829 13 -11 3 916.6696 2 -3 3 918.3159 4 919.9271 14 4 921.5052 -26 3 923.0579 2 4 924.5756 6 4 926.0589 -9 4 927.5107 -10 4 928.9306 -2 3 930.3176 8 4 931.6702 7 4 932.9890 1 5 934.2736 -12 4 935.5272 3 3 936.7448 -3 1 937.9283 -8 2 939.0769 -22 2 940.1940 -6* 7 941.2738 -17 2 9422.3170-47 1 943.3382 53* 1

I

2 2 3 3 2 4

Q(J)

o-c

I

902.7121 -26 11 902.6395 4 5 902.5329 -4 3 902.3972 1 2

J

8.5 9.5 10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5 20.5 21.5 22.5 23.5 25.5

R(J)

895.1174 896.6817 898.2093 899.7068 901.1704 902.6015 904.0002 905.3657 906.6983 907.9937 909.2621 910.4882 911.6843 912.8466 913.9754 915.0724 917.1462

2, 312 o-c

I

-8 14 -6 0 -6 -7 -2 5 16 -10 32* -10 -11 -8 4 45* -31

5 5 5 3 4 5 4 4 2 3 8 3 2 3 2 1 2

114

HAMMER ET AL. TABLE II Molecular Parameters for FO X211 Resulting from Simultaneous Analysis of All Vibrational Bands (in cm-‘) 1052.99376(24)

1.05870547(113)

Be

-0.068456(56)

B =1 B a2 x105

-O.OOlOgg1(76)

B a3 xl06

-3.009(50)

-5.945(38)

B a4 x107

-2.140(32)

De x106

4.28739(128)

1.03209(20)

D a1 x108

2.461(73)

1.445(13)

D a* x109

4.24(24)

9.90030(18)

-193.80(97)

4.34(27)

G

xl010

-0.01328015(61) -8.894(29)

1.40(23)

3.34(19) 0.014897(62)

5.55(55)

P, cl;

$x1,5

1.169(82)

a; x105

-1.19(10)

AD P* x106

1.569(38) pD x107 e

-2.05(83)

4

x104

x104

q, x105

Residual standard deviation absorption was included in the [] indicates parameter was fixed () is standard error in units of

$J

=

J

sp

[-7.01

5.2 x 10-4 cm -1. Data for 1-O fit as discussed in the text. in fit. the last digit.

w*

(19)

J’(J’ + 1) =

J

(2-7+

-2.388(50)

(.I’ + 1 + L?)(Y + 1 - n) J’t

1

(20)

Table IV shows the results of fitting the observed intensity data for 2113,2R and P branches to Eq. ( 17). Unfortunately there was no independent measurement available of the temperature of the gas within the field of view of the emission cell. Figure 5 shows a typical plot of the rotational intensity distribution of a vibrational band. Zerohlling the interferogram to obtain a sufficiently small spectral sampling interval (0.00 I 1 cm-‘) was essential for adequately determining the peak intensities. An assessment of the performance of the spectrometer may be made by comparing calculated instrumental lineshapes with observed ones as shown in Fig. 6. The measured line is an intense FO transition with a signal/noise of about 50. The interferogram was zero-filled from a 125-cm to an almost 500-cm path difference to obtain a sampling interval of 0.00 11 cm-‘. The calculated instrumental lineshape was obtained by convoluting the FO Doppler lineshape with the ideal instrumental lineshape for a true

115

IR SPECTRUM OF FO TABLE III Calculated Parameters for Specific Vibrational Bands (in cm-‘)

0”

”

a

a

A”

lo4

*D”x

a

B,

D, x 106

p, x 102

1.4775(61)

0

524.01318(8)

-193.28(97)

5.61(55)

1.0520428(11)

4.3008(11)

1

1032.96479(4)

1.06258(6)

0.148(8)

1.0385739(10)

4.3343(10)

1.4512(61)

2

1012.51163(5)

l.O9636(7)

0.180(8)

1.0248938(10)

4.3776(10)

1.4226(61)

3

991.58035(5)

1.13434(7)

0.211(8)

1.0109743(10)

4.4315(10)

1.3915(60)

4

970.12700(5)

1.17733(7)

0.242(8)

0.9967818(10)

4.4969(10)

1.3581(60)

5

948.10049(5)

1.22613(a)

0.274(9)

0.9822778(11)

4.5745(10)

1.322X(60)

6

925.44260(6)

1.28153(9)

0.305(9)

0.9674185(12)

4.6652(11)

1.2841(61)

7

902.08799(15)

1.34434(21)

0.337(9)

0.9521551(15)

4.7699(16)

1.2436(64)

8

877.96416(43)

1.4154(5)

0.368(10)

0.9364335(26)

4.8894(26)

1.2006(69)

gb

852.9915(11)

1.4954(10)

0.399(10)

0.920195(5)

5.025(5)

1.155(a)

lob

827.0832(23)

1.5852(17)

0.431(11)

0.903374(8)

5.176(7)

1.108(9)

a The are

G,,

A,,

given

and

for

AD

are

v>O wince

highly the

correlated

latter

are

and

their

differences

(i.e.,

significant to

statistically

G,

-

Gv_,)

moredecimal

places.

b Designates Note:

PD

Y

extrapolated = -2.05(83)

parameters.

x 1O-7

and

4,

= -7.0

x 10-5

(fixed)

are

the

TABLE IV Results of Fitting Rotational Intensity Distributions

1-o

334

(5)

0.873

(13)

2-l

326

(5)

0.972

(16)

3-2

329

(4)

1.190 (13)

4-3

327

(3)

1.399 (11)

5-4

330

(2)

1.283 (8)

6-5

340

(4)

0.812 (9)

7-6

342

(9)

0.340 (9)

8-7b

%rOP

0.1

Eq. (17). Absolute scale

is arbitrary. b

Estimated.

Note:

Errors in parentheses are

1 standard deviation in unit of last digit.

same

for

all

bands.

116

HAMMER ET AL.

608 w .5 E 5 c 30-

I,,,,,II,,,,,/,,,,,,,,/,,,,,,,,,

-30.5 -25.5 -20.5 -15.5 -10.5 -5.5

5.5

10.5 15.5 20.5 25.5 30.5

FIG. 5. Plot of the rotational transition intensity distribution of the P and R branches of the 4-3 2IIs,z emission band as a function of m (=J"+ I for R branch, -J” for P branch). The intensity scale has been adjusted according to Eq. (16). The solid curve represents a least-squares fit using Eq. (17) as a model. Points represented by circles were excluded from the fit due to spectral interferences.

_!

I’!‘:

943.55

I, I’

943.60

cm

CC) :::,

,’

943.65

-l

FIG. 6. Comparison of calculated and observed lineshapes for FO emission. (a) Measured 4-3 2II,,2 P( 12.5) transition. FWHM linewidth is 0.0066 cm-‘. (b) Calculated FO instrumental lineshape. FWHM linewidth is 0.005 1 cm-‘. (c) Calculated FO Doppler lineshape at T = 350 K. FWHM linewidth is 0.002 1 cm-‘.

IR SPECTRUM

OF FO

117

monochromatic line. The latter was obtained from a convolution of a sine function representing the 12%cm maximum path difference and a function representing the effect of finite aperture size. Apparently there are other factors degrading the resolution which have not been accounted for. Possible causes of the asymmetry of the measured lineshape were discussed above. These degrading effects seemed to be uniform over the entire measured spectrum and thus are not expected to affect relative intensity determinations. However, these effects would make high-resolution lineshape analysis difficult. DISCUSSION AND CONCLUSIONS

The results of this work have served not only to provide new information on the vibrational dependences of the molecular parameters of FO but also to reduce the statistical errors of those previously known. This is evident from the comparison of Table III with Table II of Ref. (1) noting that the latter gives errors in units of 3~. However, as explained in that paper, caution must be used in interpreting some of the more weakly determinable parameters. This particularly holds for the spin-orbit interaction and A-doubling parameters. An attempt to measure A directly by detecting the weak satellite bands due to *II ij2(2)‘)+ 2113,2(u”)for Au = 1 and 2 was unsuccessful. The A-doubling parameters are not all simultaneously determinable since doubling of the 2113,2transitions were not resolvable. Thus q was fixed arbitrarily to a plausible value consistent with that for other isovalent radicals. The fit did not reveal any statistically significant information on the vibrational dependence of either pD or q. With data available on higher vibrational states, additional information may be derived by employing an RKR treatment. Particularly, the indeterminancy between An and the spin-rotation parameter y may be resolved (22). Results of this study will be presented in a subsequent paper (23). As mentioned previously the exothermicity of reaction (2) is 113 kJ mole-’ or 9450 cm-’ permitting FO vibrational excitation of up to u = 10. Using a reasonable hard sphere collision cross section for FO + He, the number of collisions within the observation volume is expected to be of the order of lo4 at -0.6 Torr of He. General information on molecular energy transfer processes tends to suggest that under these conditions, translational and rotational relaxation would be complete and vibrational relaxation would be partial (24). Since the IR radiative relaxation time is much greater than the mean free time between collisions, the observed transitions should reveal translational and rotational temperatures very close to the cell temperature. This is consistent with our measurement. Rotational and spin state relaxation seems to have occurred, since the intensity data agree reasonably well with Eqs. ( 17)-(20). In principle, quantitative information on the vibrational state distribution may be obtained if experimental conditions were modified to reduce the number of collisions during observation of the emission. In conclusion, highly vibrationally excited FO emission (V f 8) has been observed at high resolution and evidence for v = 9 excitation is present in the Av = 3 spectrum. Improved molecular parameters have been obtained as well as information on the vibrational dependences of these parameters. The interpretation of the transition intensities has also been investigated. The apparatus used in this experiment has been

118

HAMMER

ET AL.

used to measure infrared spectra of numerous other radical and transient species in absorption (20, 2.5, 26). This work further illustrates the potential of the technique of high-resolution Fourier transform spectroscopy for studying such species. ACKNOWLEDGMENTS This work was supported in part by the Chemical Manufacturers Association Technical Panel on Fluorocarbon Research and by the National Aeronautics and Space Administration Upper Atmosphere and Space Services Program. The VAX 1l/750 digital computer used to carry out data reduction and analysis was acquired with the help of the National ScienceFoundation(CHE-8407084). RECEIVED:

November 6, 1987 REFERENCES

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