George W. Halsey

Diode laser spectra of the torsional splittings in the ν9 band of ethane: Torsion‐vibration‐rotation interactions and the barrier to internal rotation

Diode laser spectra of most of the Q branches of the ν9 band of ethane from RQ8–PQ15 have been recorded. The Q branches RQ0–RQ4 were deconvoluted to yield an effective resolution of (0.5–1.0)×10−3 cm−1 FWHM. Torsional splittings were observed for most lines. In contrast to predictions based on first order theory, the splittings which range from (2–53)×10−3 cm−1, have a marked J and K dependence. A second order theory of torsion‐vibration‐rotation interaction between ν9 and 3ν4 is developed, which fits the splittings with an rms error of 0.0006 cm−1, using only three adjustable parameters: the barrier to internal rotation in ν9, the energy difference between ν9 and 3ν4, and an effective coupling constant. The barrier to internal rotation in ν9 is found to be 1123±10 cm−1.

Self- and foreign-gas broadening of ethane lines determined from diode laser measurements at 12 μm

Abstract Self- and foreign-gas broadening of ethane lines have been measured in the v 9 band at 12 μm. A coefficient of 0.125 cm -1 -atm -1 was determined for self broadening. Foreign-gas broadening coefficients determined are (in cm -1 -atm -1 ) 0.090 for N 2 , 0.069 for He, 0.068 for Ar, 0.108 for H 2 , and 0.096 for CH 4 . Results are given for a sample temperature of 296 K.

High-resolution infrared spectrum and analysis of the ν9 band of ethane at 12.17 μm

Abstract The ν9 degenerate fundamental of C2H6 near 12.17 μm (822 cm−1) has been recorded at medium resolution (Δν = 0.125−0.500 cm−1) and high resolution (Δν = 0.04−0.05 cm−1) using both grating and interferometric spectrometers. The spectra have been assigned and analyzed by both standard and band contour techniques. The high-resolution spectrum showed a pronounced l-doubling in the K = 0 subband and the presence of a (2,2) type l-resonance. The assigned lines were corrected for these effects and analyzed using an energy expression through third order ( h 3 † ) with partial fourth-order ( h 4 † ) contributions. The standard deviation for the analysis of 549 of 569 assigned transitions was 6.7 × 10−3 cm−1. The ν9 band has been observed recently on Jupiter, Saturn, Titan, and Neptune by several workers. Spectra, frequency listings, and assignments have been included for use in future work on C2H6 in the atmospheres of the outer planets.

High resolution spectrum and analysis of 2ν3 of 13CH4 at 1.67 μm

Abstract The 2 ν 3 vibration-rotation overtone of 13 CH 4 near 6000 cm −1 has been recorded at 0.025-cm −1 resolution and analyzed for the first time. Nineteen spectroscopic constants have been determined with a new algorithm developed to fit simultaneously the P -, Q -, and R -branches of spherical-top molecules. This algorithm has also been used to refine the analysis of 2 ν 3 of 12 CH 4 .

Anomalous 13CH4:12CH4 line strengths in 2ν3

Unexpected and dramatic differences in transition intensities between 13CH4 and 12CH4 in the infra red spectra of methane are reported. (AIP)

Rotational parameters of the first torsional state of ethane from lower state combination differences in ν9 + ν4 − ν4

Using interferometric spectra obtained on the McMath Solar Telescope FTS spectrometer in double pass configuration (0.0025 cm−1 resolution), the ν9 + ν4 − ν4 hot band of ethane has been assigned. The torsional splittings, on the order of 0.1 cm−1, are clearly resolved. A total of 556 lower state combination differences yield the B4σ values 0.6605099(73), 0.6605005(44), 0.6604929(76), and 0.6604846(54) cm−1 for σ = 0, 1, 2, 3, respectively. D4σJ is determined to be 1.0261(68), 1.0214(37), 1.0158(49), and 1.0147(74) × 10−6 cm−1, respectively. D4σJK yields 2.741(15), 2.724(18), 2.725(13), and 2.677(18) × 10−6 cm−1. Analysis of the individual σ-state results is presented. An expression is presented which characterizes the torsional dependence of the rotational constants; coefficients in the expression are determined by least-squares analysis of the rotational constants determined from analysis of the ν9 + ν4 − ν4 band and the rotational parameters of the ground state. The B-value for 3ν4, σ = 0, is predicted to be 0.656007 cm−1 compared to a value of 0.656090(24) cm−1 in the literature. Predictions of higher excited torsional state rotational parameters are presented.

Transition moment for ν3 of 74GeH4

A vacuum grating spectrometer was used to measure the absolute line strength of the vibration‐rotation fundamental of GeHy. (AIP)

Isotope shifts in methane near 6000 cm−1

Isotope shifts for well resolved vibration‐rotation spectra of 12CH4 and 13CH4 in the 6000 cm−1 region are reported. (AIP).

Analysis of the 2ν3 band of 12CD3F at 5.06 μm recorded under high resolution

Abstract The 2 ν 3 ( A 1 ) band of 12 CD 3 F near 5.06 μm has been recorded with a resolution of 20–24 × 10 −3 cm −1 . The value of the parameter ( α B − α A ) for this band was found to be very small and, therefore, the K structure of the R ( J ) and P ( J ) manifolds was unresolved for J J values. The band was analyzed using standard techniques and values for the following constants determined: ν 0 = 1977.178(3) cm −1 , B ″ = 0.68216(9) cm −1 , D ″ J = 1.10(30) × 10 −6 cm −1 , α B = ( B ″ − B ′) = 3.086(7) × 10 −3 cm −1 , and β J = ( D ″ J − D ′ J ) = −3.24(11) × 10 −7 cm −1 . A value of α A = ( A ″ − A ′) = 2.90(5) × 10 −3 cm −1 has been obtained through band contour simulations of the R ( J ) and P ( J ) multiplets.

Analysis of the ν6(A″2) band of cyclopropane-d6 recorded under high resolution☆☆☆

Abstract The parallel band ν 6 ( A ″ 2 ) of C 3 D 6 near 2336 cm −1 has been studied with high resolution (Δ ν = 0.020 – 0.024 cm −1 ) in the infrared. The band has been analyzed using standard techniques and the following parameters have been determined: B ″ = 0.461388(20) cm −1 , D ″ J = 3.83(17) × 10 −7 cm −1 , ν 0 = 2336.764(2) cm −1 , α B = ( B ″ − B ′) = 8.823(12) × 10 −4 cm −1 , β J = ( D ″ J − D ′ J ) = 0, and α C = ( C ″ − C ′) = 4.5(5) × 10 −4 cm −1 .