R. Paso

Infrared spectrum of CO2 in the region of the bending fundamental ν2

Abstract The infrared spectrum of CO 2 in the region 540–830 cm −1 has been studied with a Fourier spectrometer at a resolution of 0.010 cm −1 . In addition to the fundamental ν 2 , more than 10 “hot” band transitions of 12 C 16 O 2 have been identified. The rotational constants involved have been derived. Special care has been taken in obtaining accurate constants for the level 01 1 0. The ν 2 fundamentals of the isotopic molecules 13 C 16 O 2 , 16 O 12 C 18 O, and 16 O 12 C 17 O have also been observed in a natural sample.

Updating OCS 2ν2 band for calibration purposes

Abstract After our previous measurement of the OCS 2 ν 2 band, which was published by Tolonen et al. in J. Mol. Spectrosc. 144 , 18–26 (1990), a clear shift has been found in the OCS ν 1 band, which was our initial calibration source. Because the lines of the 2 ν 2 band are widely used for calibration purposes, we decided to remeasure the band by calibrating it directly with the highly accurate 9.4-μm band of CO 2 . The new center of the OCS 2 ν 2 band is 1047.042051 cm −1 with an accuracy of ±6 × 10 −6 cm −1 . This value is in perfect agreement with the result from the global rovibrational analysis of OCS by Fayt et al. in J. Mol. Spectrosc. 136 , 233–266 (1986). The wavenumber list of the main band is given. The reliability of the calibration accuracy in a high-resolution commercial instrument Bruker IFS 120 HR is examined.

Analysis of the ν1 band of CH3I

Abstract The rotational structure of the infrared band ν 1 of CH 3 I has been studied at a resolution of 0.04 cm −1 using a grating spectrometer. In the analysis including 470 lines a resonance, explained to be caused by ν 2 + 2 ν 6 ±2 , has been taken into account. The molecular constants derived include, e.g., α 1 A = 0.051129(14) cm −1 and α 1 B = 0.0983(9) × 10 −3 cm −1 .

The Coriolis interaction between the fundamentals ν2 and ν5 of CD3Br

Abstract The bands ν 2 and ν 5 of CD 3 Br have been measured at a resolution of 0.010 cm −1 . They were analyzed simultaneously by taking into account the xy -Coriolis interaction. More than 1600 transitions were assigned for each isotopic species CD 3 79 Br and CD 3 81 Br. The Coriolis coupling term proved to be ζ 2,5 y = 0.559. The band centers are (in cm −1 ) ν 2 : 991.401 (CD 3 79 Br), 991.390 (CD 3 81 Br); ν 5 : 1055.474 (CD 3 79 Br), 1055.471 (CD 3 81 Br).

A high-resolution infrared study of the ν4 band of CH3I

Abstract The infrared spectrum of the ν 4 band of CH 3 I around 3060 cm −1 was studied at a resolution of 5.4 × 10 −3 cm −1 . About 1850 transitions were assigned. The K range was from K Δ K = −7 to K Δ K = +9 and the highest J values were about 75. The anomalous rotational structures observed in the subbands P Q 6 and R Q 5 – R Q 7 were explained as a consequence of Coriolis and Fermi resonances with combination levels. The standard deviation of the least-squares fit with 19 parameters was 0.00083 cm −1 . In addition to the fundamental band, the hot band ν 3 + ν 4 − ν 3 was also studied.

Overtone bands 2ν3 of 12CH3I and 13CH3I

Abstract The infrared bands 2 ν 3 of 12 CH 3 I and 13 CH 3 I have been investigated at a resolution of about 0.003 cm −1 . Both the bands, one at 1059.9934 and the other at 1028.1201 cm −1 , respectively, are very similar and they have a special feature, a bandhead, in the R branch. In both the bands about 1100 lines with J max ≈ 60 and K max = 12 have been assigned. In the analyses the model for an unperturbed parallel band could be used. In the fits the H constants fixed to ground state values have been included. Standard deviations of 0.11 × 10 −3 cm −1 and 0.13 × 10 −3 cm −1 , respectively, have been attained. Molecular constants related to the bands are given. The hot bands 3 ν 3 - ν 3 have also been studied and the results are very similar to these from the corresponding 2 ν 3 bands. The assignments of some optically pumped FIR laser lines are discussed.

Hot bands in the region of the v 5 band of HCCI: the Fermi resonance v 3 = 1/v 5 = 2

The Fourier transform infrared spectrum of monoiodoacetylene, HCCI, between 180 cm-1 and 320 cm-1 has been studied at a resolution of 0·0010 cm-1. The hot bands, v 3 ← v 1 5, 2v 0 5 ← v 1 5 and 2v 2 5 ← v 1 5, associated with the v 5 fundamental have been analysed by considering especially the Fermi resonance between the levels v 3 = 1 and v 5 = 2. The next layer of the hot bands, (v 3 + v 5)1 ← v 3, (v 3 + v 5)1 ← 2v 0, 2 5, and 3v 1, 3 5 ← 2v 0, 2 5, has been analysed by taking into account the Fermi resonance between the levels v 3 = v 5 = 1 and v 5 = 3. Also the various l responances at the overtone levels have been considered. As a result, the vibrational and rotational constants and the resonance parameters for the vibrational levels investigated have been obtained.

Perturbations in the ν1 band of CH3I

Abstract The Fourier transform absorption spectrum of CH 3 I recorded at a resolution of 0.0054 cm −1 in the region of the ν 1 band (2930–3010 cm −1 ) was analyzed. About 1600 P and R transitions were assigned for K values from 0 to 13. A Fermi interaction and two Coriolis interactions were taken into account in the analysis. The stronger Coriolis resonance, having a crossing in J in the subband K = 4 in ν 1 , is caused by ν 2 + 2 ν 6 ±2 . The other Coriolis resonance, with a matrix element of about 0.001 cm −1 , has a crossing in K between K values 10 and 11 in ν 1 . It was attributed to ν 4 . The Fermi interaction, caused probably by 2 ν 2 + ν 3 , shifts the band origin of the ν 1 band 0.6 cm −1 upward. The hot band ν 1 + ν 3 − ν 3 was also studied.

Infrared spectrum of the ν6 band of CD3Br

Abstract The infrared spectrum of the ν 6 band of CD 3 Br has been studied at a resolution of 0.010 cm −1 . The band proved to be practically unperturbed. The assignment has been extended to K ″ = 17 and J ″ = 52. Altogether about 1400 transitions for each of the isotopic species CD 3 79 Br and CD 3 81 Br were observed and they led to ν 0 values 713.472 and 713.384 cm −1 , respectively. In addition, the constants α 6 A , α 6 B , ( Aζ ) 6 , η 6 J , η 6 K , and q 6 were determined for both the isotopic molecules. The changes of the centrifugal distortion constants proved to be insignificant.

Ground-state constants A 0, D K 0 and H K 0 of 12CH3I from normally allowed infrared absorption bands

The fundamental band v 6, its hot band 2v 6-v 6 and the overtone band 2v 6 of 12CH3I were assigned. Using the lines of these three bands, ground state combination differences that differ in K by three were calculated for eight K value pairs from (3,0) to (10,7). The ground state constants A 0, D K 0 and H K 0 of 12CH3I were then determined and the results are A 0 = 5·173 9358(10)cm-1, D K 0 = 87·63(3) 10-6cm-1 and H K 0 = 4·53(22)10-9cm-1. The constant H K 0 was determined for the first time.