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Diode laser spectra of 14NH3ν2 band: Multiplets around 8.4 μm
JOURNAL
OF MOLECULAR
Diode
SPECTROSCOPY
Laser Spectra
83, 228-23 1 (1980)
of 14NH, v2 Band:
Multiplets
around
8.4 pm
High-resolution absorption spectra of 14NH, V, band have been recently investigated using tunable diode lasers, and closely spaced lines within the multiplets have been resolved and identified (I -3). In the present work the analysis of tunable diode laser spectra of three sR(J,K) multiplets (J equal to 10,ll and 12) of the r4NH, pz band in the 8.4 pm region is presented; 32 lines are resolved and identified. In the absence of secondary standards of adequate accuracy, no precise absolute line positions could be determined and therefore only intramultiplet splittings together with relative line intensities are given. The experimental apparatus used is similar to that already described in Ref. (4). Figure 1 shows the spectral features of the three multiplets investigated. The wavenumber indicated in the figure for each multiplet is a cumulative value taken from Ref. (5). The relative calibration of the intramultiplet splittings has been performed using the fringe spacing of a Germanium ttalon and the accuracy of the measurements is estimated to be r+7 x IO-* cm-*. The precision in the relative intensity values is equal to 2 10%; within each multiplet the intensities of the lines have been normalized to that of one transition set equal to 1.0. Line assignments have been obtained from line position calculations performed by using spectroscopic constants available in the literature and from expe~ment~ refative line intensity considerations. The parameters for the upper and lower states as well as those for the inversion doubling in the q state have been taken from the values obtained by Shimoda er a(. (6) from laser Stark spectroscopy measurements in the 1091-903 cm-’ region. The ground-state inversion doubling has been calculated by using Costain’s formula developed according to Ref. (7). The wavenumber values for the individual transitions have been computed including in the calculations also the sextic distortion coefficients since for a given J all the sR(J,X) components, except for the K = .I line, are separated from each other by a few hun~edths of a cm-‘. The assignments have been made through a comparison of the line separations measured and calculated using considerations on the relative line intensities as a check. As expected from theoretical considerations within each multiplet the lines corresponding to K values equal to 0, 3 or multiples of 3 show an intensity almost twice that of the nearby lines. This fact is confirmed throughout the multiplets analyzed. Anomalies for the intensities of the first line in the 1195em-’ and for the last but one line in the 1212 cm-i multiplets are explained by the occurrence in both cases of two unresolved transitions, sR(11,8) + sR(11,7) and s&12,2) + sR(12,l). respectively. Recently a paper on the Coriolis and I-type interactions in the v2, v.,, 2u,, V, + vq and 3~ states of 14NH3 by Urban ei al. (8) has appeared. The results reported by these authors for the v2 band also include the calculated positions for the sR( 10,K) and sR( 11,K) lines. Using these values the relative wavenumber differences have been included for comparison in Table I which shows our experimental results together with the suggested transition assignments. For the sR(lO,K) multiplet the agreement between the observed separations and the calculated values of Ref. (8) is good, except for the differences sR( 10,4) - sR( 10,3) and sR( 10,3) - sR( 10,9). This fact is easily explained considering that Urban et al. did not include in their calculation the AK = ?3 interactions in the vI state. The observed sR(l0,3) line has a lower wavenumber than that calculated, since the a( 11,3) level in the v2 state is pushed down by the interaction with the s( 11,O) level. For the sR(ll,K) multiplet, the agreement is satisfactory except for one case. An interchange of the sR(l1,l) and sR(11 ,O) lines is in fact suggested by the calculations of Ref. (8); however, the order as indicated in the first column of Table I is well supported by the relative line intensity values of the two transitions involved. It is interesting to note that the agreement between the observed and calculated wavenumber differences involving the sR( 11,3) transition is quite good. This is not unexpected since in the v2 state the lower inversion levels with K = 0 are missing for even values ofJ and therefore the a(l2,3) level 0022-2852/80/0~228-04$02.00/O Copyright
0 1980 by Academic
All rights of reproduction
Press. Inc.
in any form reserved.
228
229
NOTES
is not affected by the AK = ir3 perturbation with the s( 12,O)level. The line assignment in the sR( 12X) multiplet which also includes two transitions coming from the antisymmet~c levels of the ground state, needs some comments. The agreement between the experimental line wavenumber differences and those computed using the data of Refs. (6, 7) is satisfactory except for the sR(12,K) lines with K s 4 and for the aR(13,7) and aR(14,13) transitions. In spite of these discrepancies the relative line intensities lead to reasonable assignments to most of the transitions in this multiplet. Only for the
Germanium italonf.rc:O.OLS6cm-'
~1~
NH3 \)2-band 1212cm-~multiplet
W.13) aft(137)
sNt2.S) sRW.9) sRW.7)
SR(l2.6)
sR(12.4)
sR(12.10) sR~12.5)
sR112.3)
sR(12.11) SR02.2)
sR(l2.
sRR(12.0
Germanurn etalon f.+r.tIOlS7cm-~
FIG. 1. Diode laser spectra ofsR(lO,K),sR(l Ctalon fringes are also shown.
l,K), and sR(12,K) multiplets of 14NH3;the germanium
NOTES
230
TABLE I
Transition
Lineseparation (cm") exp.
Relative line intensity
Transition ref.(8)
1.0
sR (lo,71
1.7
sR (lo,61
1.2
sR (10,8)
1.1
sR 110.5)
1.0
sR i10,4b
1.7
sR (10.31
1.7
sR 110.9)
0.7
sR (10,2)
0.1
sR (lO,l)
Lineseparation (cm") talc.ref. (8)
1177.08cme' sR f10,?1 sR (10.6) st7(10,8) SR (10.51 sR (10.4) SR (lo,31 SR (10‘9) $.R(102) SR IlO,l)
0.0128 0.0341 0.0123 0.0574 0.0330 0.0368 0.0~ 0.0203
O.Ot36 0.0342 0.0138 0.0621 0.0616 0.0079 0.0429 0.0331
1195.00cm-' sR (11,8) sR (11.7) I sR (11,6) sR f11,9) sR (11.5) SR (11,4) sR (11.31 sR (ll,TO) sR (?I,21 sR Ul,l) SR (11,OJ
1.0 0.0420 0.0380 0.0305 0.0691 0.0853 0.0126 0.0432 0.0137 0.0094
sR (11.7) sR (11,8)
0.9
sR tll.6)
1.1 0.5
sR (11,S)
0.4
sR (11,4)
0.8 0.5
sR 111.3) sR (11,101
0.4
sR (11,2)
0.4
sR fll,O)
0.8
sR (11.1)
sR f11,5)
0.0011 0.0479 0.0359 0.0389 0.0822 0.0762 0.0116 0.0491 0.0212 0.0176
1212.68cm“ aR (14,13) aR (23.7) sR (12,8t sR (12.9) sR (12,71 sR (12.6) SR (12.10) sR 112,5) sR (12,4) sR (12.3) sR (12.11) sR (12,2) sR (12,ll j sR 112,121
0.0284 0.1227 0.0237 0.0130 0.0707 0.0375 0.0462 0.0837 0.0349 0.1067 0.0364
0.2 0.2 0.9 1.7 0.8 1.3 1.0 0.5 0.6 1.1 1.1 1.0
0.4425
1.2
sR(12,2) and sR(12,l) lines which
are not resolved in the spectrum and for the aR(14,13) and aR(13,7) lines which are of approximately equal intensity and lie very close to each other, the assignment indicated in Table I must be considered as tentative. ACKNOWLEDGERS The useful discussions with Dr. H. Jones and the help of G. Melandrone for the experimental measurements are acknowledged.
NOTES
231
REFERENCES I. 2. 3. 4. 5. 6. 7. 8.
J. P. SATTLER AND K. J. RITTER, J. Mol. Spectrosc. 69, 486-488 (1978). N. NERESON, .I. Mol. Spectrosc. 69, 489-493 (1978). F. CAPPELLANI AND G. RESTELLI, J. Mol. Spectrosc. 77, 36-41 (1979). G. RESTELLI AND F. CAPPELLANI, J. Mol. Struct. 60, 13-18 (1980). J. S. GARING, H. H. NIELSEN, AND K. NARAHARI RAO, J. Mol. Spectrosc. 3,496-527 (1959). K. SHIMODA, Y. UEDA, AND J. IWAHORI, Appl. Phys. 21, 181-189 (1980). E. SCHNABEL, T. TORRING, AND W. WILKE, Z. Phys. 188, 167-171 (1965). 3. URBAN, V. SPIRKO, D. PAPOUSEK, R. S. MCDOWELL, N. G. NERESON, S. P. BELOV, L. I. GERSHSTEIN, A. V. MASLOVSKIJ, A. F. KBUPNOV, J. CURTIS. AND K. NARAHARI RAO. J. Mol. Spectrosc. 79, 455-495 (1980). S. GIORGIANNI
Department of Organic Chemistry University of Venice Calle Larga S. Marta Venezia. Italy F. CAPPELLANI AND G. RESTELLI Electronics Division Department of Applied Sciences Joint Research Centre Ispra, Italy Received
January 3, 1980
OF MOLECULAR
Diode
SPECTROSCOPY
Laser Spectra
83, 228-23 1 (1980)
of 14NH, v2 Band:
Multiplets
around
8.4 pm
High-resolution absorption spectra of 14NH, V, band have been recently investigated using tunable diode lasers, and closely spaced lines within the multiplets have been resolved and identified (I -3). In the present work the analysis of tunable diode laser spectra of three sR(J,K) multiplets (J equal to 10,ll and 12) of the r4NH, pz band in the 8.4 pm region is presented; 32 lines are resolved and identified. In the absence of secondary standards of adequate accuracy, no precise absolute line positions could be determined and therefore only intramultiplet splittings together with relative line intensities are given. The experimental apparatus used is similar to that already described in Ref. (4). Figure 1 shows the spectral features of the three multiplets investigated. The wavenumber indicated in the figure for each multiplet is a cumulative value taken from Ref. (5). The relative calibration of the intramultiplet splittings has been performed using the fringe spacing of a Germanium ttalon and the accuracy of the measurements is estimated to be r+7 x IO-* cm-*. The precision in the relative intensity values is equal to 2 10%; within each multiplet the intensities of the lines have been normalized to that of one transition set equal to 1.0. Line assignments have been obtained from line position calculations performed by using spectroscopic constants available in the literature and from expe~ment~ refative line intensity considerations. The parameters for the upper and lower states as well as those for the inversion doubling in the q state have been taken from the values obtained by Shimoda er a(. (6) from laser Stark spectroscopy measurements in the 1091-903 cm-’ region. The ground-state inversion doubling has been calculated by using Costain’s formula developed according to Ref. (7). The wavenumber values for the individual transitions have been computed including in the calculations also the sextic distortion coefficients since for a given J all the sR(J,X) components, except for the K = .I line, are separated from each other by a few hun~edths of a cm-‘. The assignments have been made through a comparison of the line separations measured and calculated using considerations on the relative line intensities as a check. As expected from theoretical considerations within each multiplet the lines corresponding to K values equal to 0, 3 or multiples of 3 show an intensity almost twice that of the nearby lines. This fact is confirmed throughout the multiplets analyzed. Anomalies for the intensities of the first line in the 1195em-’ and for the last but one line in the 1212 cm-i multiplets are explained by the occurrence in both cases of two unresolved transitions, sR(11,8) + sR(11,7) and s&12,2) + sR(12,l). respectively. Recently a paper on the Coriolis and I-type interactions in the v2, v.,, 2u,, V, + vq and 3~ states of 14NH3 by Urban ei al. (8) has appeared. The results reported by these authors for the v2 band also include the calculated positions for the sR( 10,K) and sR( 11,K) lines. Using these values the relative wavenumber differences have been included for comparison in Table I which shows our experimental results together with the suggested transition assignments. For the sR(lO,K) multiplet the agreement between the observed separations and the calculated values of Ref. (8) is good, except for the differences sR( 10,4) - sR( 10,3) and sR( 10,3) - sR( 10,9). This fact is easily explained considering that Urban et al. did not include in their calculation the AK = ?3 interactions in the vI state. The observed sR(l0,3) line has a lower wavenumber than that calculated, since the a( 11,3) level in the v2 state is pushed down by the interaction with the s( 11,O) level. For the sR(ll,K) multiplet, the agreement is satisfactory except for one case. An interchange of the sR(l1,l) and sR(11 ,O) lines is in fact suggested by the calculations of Ref. (8); however, the order as indicated in the first column of Table I is well supported by the relative line intensity values of the two transitions involved. It is interesting to note that the agreement between the observed and calculated wavenumber differences involving the sR( 11,3) transition is quite good. This is not unexpected since in the v2 state the lower inversion levels with K = 0 are missing for even values ofJ and therefore the a(l2,3) level 0022-2852/80/0~228-04$02.00/O Copyright
0 1980 by Academic
All rights of reproduction
Press. Inc.
in any form reserved.
228
229
NOTES
is not affected by the AK = ir3 perturbation with the s( 12,O)level. The line assignment in the sR( 12X) multiplet which also includes two transitions coming from the antisymmet~c levels of the ground state, needs some comments. The agreement between the experimental line wavenumber differences and those computed using the data of Refs. (6, 7) is satisfactory except for the sR(12,K) lines with K s 4 and for the aR(13,7) and aR(14,13) transitions. In spite of these discrepancies the relative line intensities lead to reasonable assignments to most of the transitions in this multiplet. Only for the
Germanium italonf.rc:O.OLS6cm-'
~1~
NH3 \)2-band 1212cm-~multiplet
W.13) aft(137)
sNt2.S) sRW.9) sRW.7)
SR(l2.6)
sR(12.4)
sR(12.10) sR~12.5)
sR112.3)
sR(12.11) SR02.2)
sR(l2.
sRR(12.0
Germanurn etalon f.+r.tIOlS7cm-~
FIG. 1. Diode laser spectra ofsR(lO,K),sR(l Ctalon fringes are also shown.
l,K), and sR(12,K) multiplets of 14NH3;the germanium
NOTES
230
TABLE I
Transition
Lineseparation (cm") exp.
Relative line intensity
Transition ref.(8)
1.0
sR (lo,71
1.7
sR (lo,61
1.2
sR (10,8)
1.1
sR 110.5)
1.0
sR i10,4b
1.7
sR (10.31
1.7
sR 110.9)
0.7
sR (10,2)
0.1
sR (lO,l)
Lineseparation (cm") talc.ref. (8)
1177.08cme' sR f10,?1 sR (10.6) st7(10,8) SR (10.51 sR (10.4) SR (lo,31 SR (10‘9) $.R(102) SR IlO,l)
0.0128 0.0341 0.0123 0.0574 0.0330 0.0368 0.0~ 0.0203
O.Ot36 0.0342 0.0138 0.0621 0.0616 0.0079 0.0429 0.0331
1195.00cm-' sR (11,8) sR (11.7) I sR (11,6) sR f11,9) sR (11.5) SR (11,4) sR (11.31 sR (ll,TO) sR (?I,21 sR Ul,l) SR (11,OJ
1.0 0.0420 0.0380 0.0305 0.0691 0.0853 0.0126 0.0432 0.0137 0.0094
sR (11.7) sR (11,8)
0.9
sR tll.6)
1.1 0.5
sR (11,S)
0.4
sR (11,4)
0.8 0.5
sR 111.3) sR (11,101
0.4
sR (11,2)
0.4
sR fll,O)
0.8
sR (11.1)
sR f11,5)
0.0011 0.0479 0.0359 0.0389 0.0822 0.0762 0.0116 0.0491 0.0212 0.0176
1212.68cm“ aR (14,13) aR (23.7) sR (12,8t sR (12.9) sR (12,71 sR (12.6) SR (12.10) sR 112,5) sR (12,4) sR (12.3) sR (12.11) sR (12,2) sR (12,ll j sR 112,121
0.0284 0.1227 0.0237 0.0130 0.0707 0.0375 0.0462 0.0837 0.0349 0.1067 0.0364
0.2 0.2 0.9 1.7 0.8 1.3 1.0 0.5 0.6 1.1 1.1 1.0
0.4425
1.2
sR(12,2) and sR(12,l) lines which
are not resolved in the spectrum and for the aR(14,13) and aR(13,7) lines which are of approximately equal intensity and lie very close to each other, the assignment indicated in Table I must be considered as tentative. ACKNOWLEDGERS The useful discussions with Dr. H. Jones and the help of G. Melandrone for the experimental measurements are acknowledged.
NOTES
231
REFERENCES I. 2. 3. 4. 5. 6. 7. 8.
J. P. SATTLER AND K. J. RITTER, J. Mol. Spectrosc. 69, 486-488 (1978). N. NERESON, .I. Mol. Spectrosc. 69, 489-493 (1978). F. CAPPELLANI AND G. RESTELLI, J. Mol. Spectrosc. 77, 36-41 (1979). G. RESTELLI AND F. CAPPELLANI, J. Mol. Struct. 60, 13-18 (1980). J. S. GARING, H. H. NIELSEN, AND K. NARAHARI RAO, J. Mol. Spectrosc. 3,496-527 (1959). K. SHIMODA, Y. UEDA, AND J. IWAHORI, Appl. Phys. 21, 181-189 (1980). E. SCHNABEL, T. TORRING, AND W. WILKE, Z. Phys. 188, 167-171 (1965). 3. URBAN, V. SPIRKO, D. PAPOUSEK, R. S. MCDOWELL, N. G. NERESON, S. P. BELOV, L. I. GERSHSTEIN, A. V. MASLOVSKIJ, A. F. KBUPNOV, J. CURTIS. AND K. NARAHARI RAO. J. Mol. Spectrosc. 79, 455-495 (1980). S. GIORGIANNI
Department of Organic Chemistry University of Venice Calle Larga S. Marta Venezia. Italy F. CAPPELLANI AND G. RESTELLI Electronics Division Department of Applied Sciences Joint Research Centre Ispra, Italy Received
January 3, 1980