New spectroscopic investigations of the fourth-positive (A1Π → X1Σ+) system bands in the 13C16O molecule

Journal of Molecular Spectroscopy 266 (2011) 104–112

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New spectroscopic investigations of the fourth-positive (A1P ? X1R+) system bands in the 13C16O molecule Ryszard Keß pa, Małgorzata Ostrowska-Kopec´ ⇑, Izabela Piotrowska Atomic and Molecular Physics Laboratory, Institute of Physics, University of Rzeszów, 35-310 Rzeszów, Poland

a r t i c l e

i n f o

Article history: Received 24 March 2010 In revised form 23 February 2011 Available online 2 April 2011 Keywords: Carbon monoxide Fourth-positive system CO molecule Perturbations

a b s t r a c t The present work puts forward the results of the recordings carried out under high resolution by conventional, photographic spectroscopy and modern analysis of thirteen bands with v0 = 7–12 and v00 = 16–24 of the fourth-positive (A1P ? X1R+) band system. The current investigations include the region of the observed 13C16O molecule spectrum, much greater now than before. Especially, new transitions connected with not hitherto observed v0 = 12 vibrational level of the A1P state, were recorded and studied. Moreover, the region of perturbations observed in the upper state of the fourth-positive system was significantly enlarged. The observed perturbations were confronted with those predicted from theoretical calculations. Ó 2011 Elsevier Inc. All rights reserved.

1. Introduction CO is one of the most stable small diatomic molecules and one of the most common molecules in the Universe, after H2. It is also still one of the most explored small molecules, both theoretically and experimentally. For years in succession the laboratory studies of the CO spectrum have focused on its highly excited electronic states. The first of singlet excited states, the A1P state, is accessible to explore, for example, through the analyses of bands of the fourth-positive (A1P ? X1R+) system. The A–X system is a dominant feature in the astrophysically observed VUV spectra and accurate laboratory spectral data of its spectral lines are extremely required. Considerably greater part of such investigations is concerned with the ordinary 12C16O molecule, than with the other isotopic species of CO. Especially, when it comes to the 13C16O molecule, which also plays an important role in the astrophysics, we have little information devoted to its energetic structure and particularly to its A1P ? X1R+ transition spectrum. The first communication about observation of several absorption bands, belonging to fourth-positive system in 13C16O, dates from 1929 [1]. McCulloh and Glockler [2] were the first who published the bandheads’ wavenumbers of 35 emission bands (involving v0 = 2–10 and v00 = 9–21) of the A–X transition in 13C16O. The spectrum was recorded under low resolution, and due to the perturbations and overlapping of bands the precision of the wavenumbers was not great. In turn, basing on the observations of electronic, high-resolution absorption spectra, Tilford and Simmons [3] in 1972 presented the measurements of bandheads of A–X transi-

⇑ Corresponding author. E-mail address: [email protected] (M. Ostrowska-Kopec´). 0022-2852/$ - see front matter Ó 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.jms.2011.03.008

tion bands in 13C16O. They involved v0 = 2–16 and v00 = 0 vibrational levels and the region of spectrum with wavelengths shorter than 2000 Å. Then, Domin [4] conducted vibrational-rotational analyses of 28 emission bands of A–X system in this molecule. The bands involved v0 = 3–11 vibrational levels of the upper A1P state and v00 = 12–22 vibrational levels of the ground X1R+ state, with low and medium rotational J levels. The analyses of bands and calculations of selected molecular parameters of the A1P state, performed by the author, were partial and rather preliminary. Next, the results of spectroscopic research relative to the fourth-positive system in the 13C16O molecule were presented by Haridass and Huber [5]. The analyses involved wavelengths from 1370 to 1600 Å and were concerned with transitions between v0 = 0–9 levels of the upper electronic state and v00 = 0–5 levels of the lower state. Du Plessis et al. [6,7] was the first who recorded each time a few spectral lines of the A1P(v0 = 0–5)–X1R+(v00 = 0) transitions in four isotopic molecules: 12C16O,13C16O,12C17O and 12C18O. Recently, Domin et al. [8] recorded and partly analysed two bands of the A1P ? X1R+ system in 13C16O, namely 11–21 and 11–22 bands. As the history of the fourth-positive system investigations into CO shows, we still lack information about spectrum, terms and molecular parameters describing the highly excited rovibronic A1P state of 13C16O. Taking into account this scientific gap, we present the results of the new and the extended observations and analysis of the fourth-positive system including thirteen bands (7–16, 7–18, 8–17, 8–19, 8–20, 9–19, 9–20, 10–20, 10–21, 11–21, 11–22, 12–23 and 12–24) and nearly 1200 spectral lines. The 12–23 and 12–24 bands were observed, recorded and analysed for the first time. In the other bands the number of the spectral lines as well as the region of the recorded rotational levels was extended nearly twice in comparison with the earlier analyses. For all analysed bands their band heads were determined – seven of

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thirteen band heads were received for the first time. The merge fitting of all analysed bands provided a set of accurate effective rovibronic molecular parameters and band origins. It is worth mentioning that eight (B8, B10, B12 and Dv constants for v = 8–12 levels) of the twelve rotational constants of the A state were received for the first time. Furthermore, the band origins of the 12–23 and 12–24 bands were obtained for the first time and when it comes to the other bands, the accuracy of the band origins were improved no less than ten times in comparison with the earlier analyses. Finally, the real values of the A1P state rovibrational terms were calculated. Notice, for vA = 10–12 levels the actual values of the rotational terms were obtained for the first time. There is still a problem of the structure regularity of the A1P state and the need of verification of the perturbation interactions of this one and six other electronic states, which are localized in the spectral region of 60 000 cm1: I1R, D1D, e3R, a0 3R+, d3Di and a3Pr. Therefore, we present the results of the observations and identifications of perturbations in all investigated here A1P v = 7–12 levels of 13C16O. Notice that perturbations of v = 7, 9 and 12 levels are observed for the first time. When it comes to v = 8, 10 and 11 levels, the number of perturbating states and the places of perturbation occurrence is verified and filled in. 2. Experimental details The emission spectrum of the A–X system bands was excited in the water-cooled Geissler type tube filled with commercial gaseous carbon monoxide enriched in about 90% of the 13C isotope. Gas pressure in the lamp was about 0.2 kPa. The tube was operated at about 3.5 kV and 100–200 mA AC. The exposures were taken on a 2–m Ebert spectrograph PGS-2, equipped with 651 grooves/mm reflection diffraction grating with a total of 45 600 grooves. The exposures were performed in the 10th order with the reciprocal linear dispersion of about 0.040 nm/mm and the theoretical and approximately observed resolution of 450 000. The exposure time on the ORWO UV-1 spectral plates varied from 8 to 10 h. As a calibration spectrum, we used the Th standard lines [9] obtained from a water-cooled hollow-cathode tube. The relative positions of the lines were measured by using a laser-interferometric comparator with the accuracy better than 0.5 lm. Assuming the Gaussian profile for each spectral line contour and making use of the leastsquares method, the position of each line center was calculated by means of an interactive graphic computer program, created in our laboratory. The compressed view of the high-resolution spectrum of the 9–19 band of the A1P ? X1R+ system in 13C16O is presented in Fig. 1a. The part of this spectrum surrounded by a rectangle is shown in Fig. 1b. The full width at half maximum of the line marked by an asterisk in Fig. 1a is ca 0.2 cm1 and the signal-to-noise ratio for that line is about 15. The estimated rotational temperature for the 9–19 band of the A–X system in 13C16O is 600 K. The estimated precision of the wavenumber of the single spectral line is considered to be in the range of 0.020–0.030 cm1. As a result of the exposures, thirteen bands with the upper v0 = 7–12 and lower v00 = 16–24 levels were recorded. The total number of the spectral lines was about 1200. The statistical information about the bands analysed in this work is collected in Table 1 and the experimental wavenumbers are deposited in the Electronic Depository of the Supplementary Material of the journal. 3. Analyses and calculations 3.1. Wavenumbers and terms The vibrational–rotational analysis of each band structure started by determining the upper and the lower vibrational level

and ascribing the proper quantum number J value to each spectral line, as well as assembling all the lines into P, Q and R branches. It was executed on the basis of the analyses’ results of Domin [10] and the application of typical spectroscopic methods [11]. The intrasystem vetting of correctness of these interpretations, especially useful in the highly perturbed regions of spectrum, was performed by employing the Jenkins–McKellar method [11] (p. 188) for the bands with a common upper vibrational level. On the basis of the spectral lines’ wavenumbers and the molecular parameters of the rovibrational structure of the X1R+ state, the average rotational terms’ values of the explored levels of the A1P state were calculated. The necessary parameters of the X1R+ state were obtained by the isotopic recalculations of the constants of the 12C16O molecule received by Le Floch [12]. The terms values were estimated against J = 0 of v = 0 level of the ground X1R+ state. They are deposited in the Electronic Depository of the Supplementary Material of the journal. 3.2. Perturbations of A1P state in

13 16

C O

The A1P electronic state of the CO molecule is extensively and intensively perturbed by the other electronic states, located nearby. One can actually observe the perturbations of the rotational structure in each vibrational level. They were very often a subject of the analyses during the studies of different band systems involving the A1P state, like B1R+ ? A1P (Ångström band system) [13–15], C1R+ ? A1P (Herzberg band system) [16], E1P ? A1P (Ke ß pa–Rytel band system) [17]. For 12C16O many perturbations have been reported. A systematic classification of the A1P state perturbations observed up to 1966 was carried out by Krupenie [18] and completed by Simmons et al. [19]. A comprehensive analysis and a deperturbation calculation for the A1P state in 12C16O on the basis of the data obtained up to 1971 were performed by Field [20] and Field et al. [21]. They were the first who provided deperturbed vibrational and rotational equilibrium parameters of the A1P and six (I1R, D1D, e3R, a0 3R+, d3Di and a3Pr) nearby states. Le Floch et al. [22] conducted an extensive study of the A1P v = 0 state perturbations. Le Floch [23] performed perturbation calculations for the A1P v = 0–4 state. Finally, Le Floch [24] collected the exact term values for A1P v = 0–8 state of 12C16O. There have been comparatively few explorations of the A1P perturbations in 13C16O. There are two papers, however, in which the perturbation analysis results of the A state are presented on the basis of the investigations of the fourth-positive band system in the 13C16O molecule. Firstly, Domin [4] identified some rotational perturbations of a mere four (v0 = 6, 8, 10, 11) from all observed by him levels of the upper A1P electronic state. Secondly, Haridass and Huber [5] observed perturbations in A1P v = 0, 1, 2, 5, 6 levels and analysed two of them, in v = 0 and v = 6 levels. They investigated the perturbation of A1P, v = 0 by e3R, v = 1 as well as the perturbation of A1P, v = 6 by d3Di, v = 12 and evaluated the percentage 1P character in the mixed A state v = 0 and v = 6 levels, for low and medium rotational quantum number J values. Ke ß pa et al. [15] observed the perturbations of A1P v = 0–6 state 13 16 of C O by the analysis of the Ångström (B1R+ ? A1P) system. They calculated the theoretical points of perturbations for v = 0– 10 levels. This work presents the results of the observations and identifications of perturbations in the A1P v = 7–12 levels of 13C16O. Notice that perturbations of v = 7, 9 and 12 levels were studied for the first time. Aiming at following the regularity of the rotational structure of the A1P state in the observed region of vibrational levels, and paying special attention to v = 12 level, which has not been studied until now, the effort of identifying the numerous perturbations of this state was undertaken. During these analyses we admitted as

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R. Keßpa et al. / Journal of Molecular Spectroscopy 266 (2011) 104–112

(a)

(b)

Fig. 1. (a) A compressed view of the high-resolution spectrum of the 9–19 band of A1P ? X1R+ system in spectrum, together with the rotational interpretation.

Table 1 Summary of observations of the fourth-positive (A1P ? X1R+) band system in Band 7–16

43197.98c 43197e 39873.45c 39873.4e 38247.69c 38247.3e 41057.29c

11–21

39431.30c 39431.4e 40582.19c 40586e 38979.88c 38982e 40099.11c

11–22

38520.68c

12–23 12–24

c

9–20 10–20 10–21

c

e

c

8–17

9–19

d

43679.22

c

40306.89

8–20

a

Band head (in cm

7–18

8–19

b

1

38053.11 36522.03c

)

a

C O.

Band origin (in cm 43669.5350(21) 43668.14d 40295.2179(36)c 40294.12d 43188.871(20)c 43188.32d 39862.782(16)c 39862.29d 38235.912(20)c 38235.18d 41048.0726(37)c 41046.77d 39421.1594(51)c 39419.82d 40573.6530(99)c 40572.56d 38970.6468(94)c 38969.50d 40091.246(11)c 40090.04d 38512.165(11)c 38510.95d 38044.9927(78)c 36513.2031(59)c

C O. (b) An expanded part of the emphasized piece of this

13 16 1

c

13 16

)

Jmax

rf  102 b (in cm1)

79

32

0.34

100

36

1.57

75

29

1.78

81

33

1.18

81

33

1.62

118

42

1.84

110

39

1.87

90

34

3.52

86

30

2.89

102

38

3.03

102

38

2.87

88 88

36 36

2.56 2.27

Total number of lines

Values from final merging; uncertainties in parentheses represent one standard deviation in units of the last quoted digit. Standard deviations of individual band fits. This work. After Domin [4]. After McCulloh and Glockler [2].

R. Keßpa et al. / Journal of Molecular Spectroscopy 266 (2011) 104–112

107

Fig. 2. Values of rovibronic terms of the perturbed A1P v = 11 and 12 levels together with perturbing I1R (v = 16–18), D1D(v = 15–17), e3R (v = 16–18), a0 3R+ (v = 25–27), d3Di (v = 19–21) and a3Pr (v = 22, 23) levels of 13C16O versus J(J + 1). Points of crossings show the positions of expected perturbations. Compare Table 2.

Fig. 3. Plot of deviations [T(v, J)obs  T(v, J)calc] of the A1P

v = 7–12 rovibrational levels versus J in 13C16O.

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Table 2 Observed and predicted perturbations of the A1P state levels in Perturbed level (v)

13 16

C O.a,b,c

Maximum of perturbation (J) of the K-doubling component

Perturbing state

f

Triple component

Vibrational level

F(1) F(2) F(3)

e3R (v = 11)

31

F(1) F(2) F(3)

a3R+ (v = 19)

33 37 41

F(3) F(2) F(1)

Observed

e Calculated

7 29

Observed

Calculated

27

26

29 32

28

28 31

34

34

33

33 37 41 40

8

D1D (v = 10)

40 <1

1

F(2) F(3) F(3) F(2) F(1)

4

4

16 20 25

15–16 19–20 23–24

16 20

15–16 19–20 23–24

21

22–23

21

22–23

25 30

25 29 33

25 29 33

F(1) F(2) F(3)

13

12

30

29

36

35

36

36

F(1) F(2) F(3)

a0 3R+(v = 21)

9

5–6 9–10 13–14

F(1) F(2) F(3)

a3Pr (v = 20) I1R (v = 13)

33

32

34

33 39

10

a3Pr (v = 19)

44–45 47–48 5–6 9–10 13–14

d3Di (v = 15)

I1R (v = 12)

41–42

7

a3R+(v = 20)

D1D (v = 11)

35

9

d3Di (v = 14) a3Pr (v = 18)

F(1) F(2) F(3)

a0 3R+ (v = 22)

F(1) F(2) F(3)

e3R (v = 14) D1D(v = 13)

40

40–41

40–41

37 41

38 42 46

38 42 46

F(3) F(2) F(1)

d3Di (v = 17)

8

6 10

9

F(1) F(2) F(3)

a0 3R+ (v = 23)

15

15–16

e3R (v = 15)

21

21–22

F(1) F(2) F(3)

13

12

19

18–19

26

25

25–26

25

26–27 30–31 33–34

25–26 29–30 33–34

26–27

25–26 29–30 33–34

D1D (v = 14) F(3) F(2) F(1)

I1R (v = 15)

36 41–42 44–45

F(1) F(2) F(3)

a0 3R+ (v = 24)

<1 2 6

F(3) F(2) F(1)

d3Di (v = 19)

47–48 11 10

<1 2 6

18–19

18

30

29

10

I1R (v = 16) 32

35

d3Di (v = 18)

32

35 37–38 40–41 43–44

F(1) F(2) F(3) F(1) F(2) F(3)

a0 3R+ (v = 25) e3R (v = 17) D1D (v = 16)

109

R. Keßpa et al. / Journal of Molecular Spectroscopy 266 (2011) 104–112 Table 2 (continued) Perturbed level (v)

Maximum of perturbation (J) of the K-doubling component f

12

e

Observed

Calculated

9

7

14

13

21–22

20

26–27

26–27

31 35

Perturbing state

31 35 39

Observed

Calculated

11

10

21

20

24

23–24

Triple component

Vibrational level

F(1) F(2) F(3)

a0 3R+ (v = 26) D1D (v = 17) e3R (v = 18)

29–30

F(1) F(2) F(3)

31 35 39

F(3) F(2) F(1)

d3Di (v = 21) I1R (v = 18)

36–37 39–40 42–43

F(1) F(2) F(3)

15 19 23

F(3) F(2) F(1)

30–31

F(1) F(2) F(3)

45–46 13

15 19 23 27–28 33–34 38–39 43–44

46–47 14

1–2 4–5 7–8 22

27–28 33–34

e3R (v = 20)

F(1) F(2) F(3)

a0 3R+ (v = 29) D1D (v = 20)

F(1) F(2) F(3)

34 38 42

F(3) F(2) F(1)

d3Di (v = 24)

40

F(1) F(2) F(3)

a0 3R+ (v = 30)

F(1) F(2) F(3)

e3R (v = 22)

37 43 15

5 8 11

I1R (v = 22)

15 18 22 26

18 22 26

F(1) F(2) F(3)

a3Pr (v = 27)

20–21 24–25 28–29

20–21 24–25 28–29

F(3) F(2) F(1)

d3Di (v = 25)

27

F(1) F(2) F(3)

a0 3R+ (v = 31)

24 30 35–36

D1D (v = 22)

35–36

I1R (v = 23)

42 41–42 44–45 47–48 a

e3R (v = 21) I1R (v = 21)

33–34 34 38 42

a0 3R+ (v = 28)

F(1) F(2) F(3)

22

30–31

d3Di (v = 22) I1R (v = 19)

D1D (v = 19)

38–39 40–41

a0 3R+ (v = 27)

F(1) F(2) F(3)

e3R (v = 23)

Observed perturbations for the v = 0–6 levels can be found in Refs [13,16]. Observed perturbations for the v = 7–12 levels are from this work. Predicted perturbations were calculated by using constants of Field [20] for A1P, I1R, e3R, a0 3R+, d3Di and a3Pr states and of Kittrell and Garetz [26] for D1D state, isotopically recalculated for the 13C16O molecule. b

c

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R. Keßpa et al. / Journal of Molecular Spectroscopy 266 (2011) 104–112

highly significant the incorporation of the a3Pr state into the group of states which perturb the A1P state. So far, the a3Pr state has never been considered as a perturber of the A1P state. Hence, making a test of its influence on A1P state could considerably improve the knowledge about the observed perturbations in this state, and establish an appropriate and complete perturbation matrix of the A1P state levels. Considering the fact, that the identification of the A1P state perturbations was performed fragmentarily as yet and it is incomplete, we compared the perturbations calculated with the observed ones. To begin with, the positions of the predicted perturbations were estimated on the basis of rovibronic terms’ plots of the perturbing I1R, D1D, e3R, a0 3R+, d3Di and a3Pr states together with the perturbed A1P state. The points of intersections of these plots correspond the places for which the strongest perturbations are expected. Garetz et al. [25] constructed such a diagram for 12 16 C O, determining the crossings of the A1Pv = 0–13 levels with the nearby states. Fig. 2 presents a piece of our diagram, involving the perturbed A1P v = 11 and 12 levels and perturbing I1R (v = 16–18), D1D (v = 15–17), e3R (v = 16–18), a0 3R+ (v = 25–27), d3Di (v = 19–21) and a3Pr (v = 22, 23) levels. The term values of the levels studied were calculated in the range of J = 1–40 by the isotopic recalculations of the rovibronic structure parameters, which in turn were obtained for the A1P, I1R, e3R, a0 3R+, d3Di and a3Pr states by Field [20] and for the D1D state by Kittrell and Garetz [26]. Next, the places of occurrence of the observed perturbations were determined following the course of fx (J) and gx (J) functions, where x = Q, PR and PR, introduced by Kovács [27]. The deviations from the regularity of these functions’ course indicated the appearance of some specific perturbation interactions and enabled the localization of the observed perturbation. The identification of the perturbing state was made by analyses of correlations between these residuals in the mentioned functions’ courses and the selection rules for perturbations [28,27]. The perturbation occurrence in the rotational structure of the observed bands can also be directly exhibited by a plot of the deviations [T(v, J)obs  T(v, J)calc] versus the rotational quantum number J. Such plots for the A1P, v = 7–12 levels of 13C16O are shown in Fig. 3. As one can see, more or less strong discontinuities occur at different J values for each vibrational A1P level. These are characteristic of the observed perturbations. There is a noticeable correspondence between Fig. 3 and Table 2. It is easily seen for v = 11, J = 10, in both e/f parity components, for example. The comparison of the observed perturbation with these predicted on the basis of the theoretical calculations can be found in Table 2. We have collected here all known observed perturbations as well as the computed ones for A1P v = 7–15 levels. The respective perturbations for A1P v = 0–6 levels can be found in Refs. [13,16]. For each perturbed A1P vibrational level, Table 2 gives J value, for which the strongest perturbation occurs in both the e/f parity components, and respective perturbing vibrational level. It is worth mentioning, that perturbations of the A1P v = 7, 9 and 12 levels have not been investigated before. 3.3. Molecular parameters The further vibrational–rotational analyses of the bands as well as their reduction to the molecular parameters run thanks to a wide-known theoretical model, in which both states participating in the explored transition are represented by the proper hamiltonians; for both K-components of the A1P state

hHi ¼ T v þ Bv ½JðJ þ 1Þ  1  Dv ½JðJ þ 1Þ  12 þ    ;

ð1Þ

and for the X1R+ state

hHi ¼ G0 ðv Þ þ Bv JðJ þ 1Þ  Dv J 2 ðJ þ 1Þ2 þ    ;

ð2Þ

where Tv and G0(v) are the rotationless energies for the A1P and X1R+ states, respectively. They are calculated with respect to the lowest rovibrational level in the ground X1R+ state.

Table 3 Rotational constans Bv and Dv (in cm1) for the A1P state levels of the 13C16O molecule.a v

Dv  106

Bv b

1.380141(28) 1.37743(76)c 1.380473(82)d 1.380335e

7.715(49)b

8

1.355247(90)b 1.357655e

7.89(21)b

9

1.334587(16)b 1.33143(57)c 1.334799e

7.741(14)b

10

1.314359(51)b 1.311772e

10.533(68)b

11

1.290028(50)b 1.2791(2)f 1.288544e

9.244(51)b

12

1.265512(62)b 1.265042e

9.41(11)b

7

8.50(21)d

a Uncertainties in parentheses represent one standard deviation in units of the last quoted digit. b This work. c After Domin [4]. d After Ke ßpa et al. [15]. e Recalculated from the 12C16O data of Field [20] using the isotopic relationships. f After Domin et al. [8].

Table 4 Equilibrium molecular constants (in cm A1P state of the 13C16O molecule.

1

) of the

Constant

Valuea

xe

1484.154(53)b 1484.94(49)c 1486.659d

xexe

16.911(11)b 17.054(85)c 19.166d

xeye  102

2.336(53)b 3.165(10)c 79.7d

Be

1.54263(71)b 1.5451(13)c 1.544027d

ae  102

2.059(46)b 2.245(21)c 2.008d

ce  104

1.687(76)b 9.2d

e  105

0.339(36)b 27.3d

a Uncertainties in parentheses represent one standard deviation in units of the last quoted digit. b This work. c After Domin [4]. d After Field [20]; the values recalculated from the data for the 12C16O molecule, using isotopic relationships.

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R. Keßpa et al. / Journal of Molecular Spectroscopy 266 (2011) 104–112 Table 5 Franck–Condon factors of the fourth-positive band system of

13 16

C O.

v0 nv00

16

17

18

19

20

21

22

23

24

25

7 8 9 10 11 12 13 14 15

9.974E02 3.865E02 5.634E03 5.349E02 3.929E03 3.483E02 8.201E03 2.314E02 9.181E03

8.527E02 8.583E02 1.073E02 2.563E02 4.215E02 1.361E03 4.015E02 1.459E05 2.818E02

5.308 E02 9.570E02 5.895E02 1.007E05 4.504E02 1.997E02 1.491E02 2.851E02 8.807E03

2.582E02 7.197E02 9.292E02 2.871E02 8.266E03 5.041E02 2.843E03 3.097E02 1.035E02

1.021E02 4.075E02 8.691E02 7.622E02 6.503E03 2.739E02 3.865E02 1.660E03 3.550E02

3.365E03 1.835E02 5.803E02 9.301E02 5.002E02 1.751E04 4.405E02 1.815E02 1.498E02

9.396E04 6.788E03 2.996E02 7.473E02 8.704E02 2.287E02 1.006E02 4.740E02 2.603E03

2.249E04 2.107E03 1.249E02 4.469E02 8.681E02 6.915E02 4.298E03 2.847E02 3.539E02

4.654E05 5.568E04 4.322E03 2.113E02 6.100E02 9.018E02 4.379E02 5.733E04 4.356E02

8.371E06 1.265E04 1.263E03 8.172E03 3.295E02 7.607E02 8.227E02 1.883E02 1.130E02

It is a well-known fact, that the A1P state is widely and intensively perturbed, whereas the X1R+ state is regular in the presently studied region. That is why, the calculation of the molecular constants was performed in stages and by means of several methods. At the first stage of the calculations, during individual band fittings, only the Bv and Dv rotational constants of the lower X1R+ state levels were computed. The main aim of this procedure was verifying the assumed rotational structure of bands, especially in extensively and multistate perturbed areas. To this end, the method proposed by Curl and Dane [29] and Watson [30] was used, because this procedure makes it possible to separate the information concerning the upper and the lower states of the observed electronic-vibrational– rotational transitions. The obtained in this way rotational constants of the X state levels confirmed the correctness of our rotational interpretation, as they corresponded with the values recalculated isotopically from the constants received by Le Floch [12]. In further calculations we decided to use the latter ones, however, since the parameters of Le Floch [12] seem to be commonly known as the most precisely calculated molecular constants of the X1R+ state of the CO molecule. At the second stage of the molecular parameters’ calculations the effective Bv and Dv rotational constants of the upper A1P state levels as well as band origins of the A1P ? X1R+ transition were obtained. It was executed using the X1R+ state constants, recalculated from Le Floch [12] data (as we mentioned earlier), and on the basis of the least-squares method. During these estimations we used carefully selected spectral lines without any noticeable effects of the perturbational interactions. The final values of the rotational structure parameters of the studied A1P state were achieved at the third stage of the calculations, as a result of the merge fitting of all analysed bands, according to the procedure proposed by Albritton et al. [31] and Coxon [32]. In this method, the fitted bands have to have the common upper or lower vibrational level. For each band, the molecular constants of its lower vibrational level were fixed to the values obtained from Le Floch [12] parameters. Therefore, the merge fitting of the analysed bands consisted of six parts: each of them covered a group of bands with the common upper v0 = 7–12 level. The estimated variances of these mergings were: r2v 0 ¼7 ¼ 2:58; r2v 0 ¼8 ¼ 0:67; r2v 0 ¼9 ¼ 1:51; r2v 0 ¼10 ¼ 0:55; r2v 0 ¼11 ¼ 2:67 and r2v 0 ¼12 ¼ 2:57, respectively. The rotational parameter values derived for the explored levels of the A1P state are gathered in Table 3, whereas the calculated band origins are presented in the third column of Table 1. Notice, the constants of v0 = 12 were obtained for the first time. Basing on generally known dependencies of the rovibronic parameters upon the ðv þ 12Þ argument and fixing during calculations the values of the lower X1R+ state constants, we computed the equilibrium vibrational and rotational constants of the studied upper A1P state. The results are collected in Table 4. Next, the Franck–Condon factors for the selected bands of the A1P ? X1R+ transition of 13C16O were estimated. It was executed employing

the calculated equilibrium molecular parameters of the A1P state as well as the constants of the X1R+ state, which were isotopically recalculated on the basis of the most precisely computed constants of 12C16O [12]. They are listed in Table 5. 4. Discussion and conclusions The current work presents the results of the new observations under high resolution, precise measurements and modern analyses of the thirteen bands with v0 = 7–12 and v00 = 16–24 levels of the A1P ? X1R+ transition in the 13C16O molecule. The application of high resolution and the great precision of the measurements enabled us to calculate the set of the molecular constants and outline the first complete characteristic of the upper A1P state of the fourth-positive system. On the basis of the wavenumbers of the analysed bands’ spectral lines and the X1R+ state rotational parameters, we were able to calculate the real values of the A1P state rovibrational terms. A careful investigation of the Kovács functions’ course allowed us to confirm the occurrence of the great part of the predicted rotational perturbations. The respective J values in Table 2 show the great consistency of the observed perturbations and the expected ones. Notice, we were the first in present analysis to regard the a3Pr state as the perturber of the A1P state. We attempted to test the influence of the former of them on the levels of the latter one. After our studies, we are sure about a3Pr state effect on the A1P v = 8 and v = 9 levels. In other cases it is hard to unequivocally explain, which state is the perturbation’s reason. We hope, however, that our analyses will become the impulse to the following investigations of this isotopic molecule. Appendix A. Supplementary material Supplementary data for this article are available on ScienceDirect (www.sciencedirect.com) and as part of the Ohio State University Molecular Spectroscopy Archives (http://library.osu.edu/sites/ msa/jmsa_hp.htm). Supplementary data associated with this article can be found, in the online version, at doi:10.1016/ j.jms.2011.03.008. References [1] [2] [3] [4] [5] [6]

R.T. Birge, Phys. Rev. 34 (1929) 379. K.E. McCulloh, G. Glockler, Phys. Rev. 89 (1953) 145–147. S.G. Tilford, J.D. Simmons, J. Phys. Chem. Ref. Data 1 (1972) 147–187. J. Domin, Acta Phys. Hung. 60 (1986) 43–49. C. Haridass, K.P. Huber, Astrophys. J. 420 (1994) 433–438. A. Du Plessis, E.G. Rohwer, C.M. Steenkamp, Astrophys. J. Suppl. S. 165 (2006) 432–437. [7] A. Du Plessis, E.G. Rohwer, C.M. Steenkamp, J. Mol. Spectrosc. 243 (2007) 124– 133. [8] J. Domin, P. Malita, D. Rylska, Proc. SPIE 6937 (2008) 1–4. [9] B.A. Palmer, R. Engleman Jr., Atlas of the Thorium Spectrum, Los Alamos National Laboratory, Los Alamos, NM, unpublished .

112

R. Keßpa et al. / Journal of Molecular Spectroscopy 266 (2011) 104–112

[10] J. Domin, Private communication. [11] G. Herzberg, Molecular Spectra and Molecular Structure, Krieger Publishing Company, Malabar, 1950. [12] A.C. Le Floch, Mol. Phys. 72 (1991) 133–144. [13] M. Rytel, Acta Phys. Pol. A 37 (1970) 559–568. [14] J. Janjic´, J. Danielak, R. Ke ßpa, M. Rytel, Acta Phys. Pol. A 41 (1972) 757–761. [15] R. Ke ß pa, U. Domin, K. Porada, Acta Phys. Pol. A 103 (2003) 441–451. [16] R. Ke ß pa, Acta Phys. Hung. 45 (1978) 133–147. [17] R. Ke ß pa, M. Rytel, Z. Rzeszut, Acta Phys. Pol. A 54 (1978) 355–361. [18] P.H. Krupenie, The Band Spectrum of Carbon Monoxide, Nat. Bur. Stand., NBS5, Washington, DC, 1966. [19] J.D. Simmons, A.M. Bass, S.G. Tilford, Astrophys. J. 155 (1969) 345–358. [20] R.W. Field, Ph.D. Thesis, Harvard University, 1971. [21] R.W. Field, B.G. Wicke, J.D. Simmons, S.G. Tilford, J. Mol. Spectrosc. 44 (1972) 383–399.

[22] A.C. Le Floch, F. Launay, J. Rostas, R.W. Field, C.M. Brown, K. Yoshino, J. Mol. Spectrosc. 121 (1987) 337–379. [23] A.C. Le Floch, Ph.D. Thesis, University Paris-Sud, Orsay, 1989. [24] A.C. Le Floch, J. Mol. Spectrosc. 155 (1992) 177–183. [25] B.A. Garetz, C. Kittrell, A.C. Le Floch, J. Chem. Phys. 94 (1991) 843–853. [26] C. Kittrell, B.A. Garetz, Spectrochim. Acta A 45 (1989) 31–40. [27] I. Kovács, Rotational Structure in the Spectra of Diatomic Molecules, Akadémiai Kiadó, Budapest, 1969. [28] R. de L. Kronig, Z. Phys. 50 (1928) 347–362. [29] R.F. Curl, C.B. Dane, J. Mol. Spectrosc. 128 (1988) 406–412. [30] J.K.G. Watson, J. Mol. Spectrosc. 138 (1989) 302–308. [31] D.L. Albritton, A.L. Schmeltekopf, R.N. Zare, J. Mol. Spectrosc. 67 (1977) 132– 156. [32] J.A. Coxon, J. Mol. Spectrosc. 72 (1978) 252–263.