S.J. Daunt

10 mu m ethylene: spectroscopy, intensities and a planetary modeler's atlas

FTS and TDL spectra of ethylene in the 10 mum region have been observed, measured, calibrated, assigned and intensities have been measured. The ultimate goal of this work is the production of a planetary modelers atlas. A spectrum taken in double-pass configuration at the McMath-Pierce FTS instrument at Kitt Peak National Observatory has been frequency calibrated using CO2 laser bands. Results of a previous analysis (Cauuet et al., J Mol Spectrosc 1990;139:191) have enabled the assignment of the FTS spectrum wherein we have measured over 500 line intensities in the 900-1000 cm(-1) region. These FTS intensities have been calibrated against 13 isolated transitions, taken as secondary intensity standards. These standard lines have been measured independently using TDL (tunable-diode-laser) spectrometers at University of Tennessee and Goddard Space Flight Center. A calculated spectrum, including mixing coefficients for v(4), v(7), v(10) and v(12), and calculated relative intensities, and the TDL-calibrated FTS line intensities were used as data in a non-linear regression analysis to determine the 296 K vibrational band intensities of S-0-7(v) = 321.69 +/- 0.36 cm(-1)/cm atm, S-0-10(v) = 1.16 +/- 0.47 cm(-1)/cm atm, and S-0-12(v) = 31.60 +/- 9.80 cm(-1)/cm atm. These vibrational band intensities combined with the theoretical spectral-line atlas make possible the generation of an ethylene spectrum at an arbitrary temperature. Such spectra prove useful to the planetary-atmosphere modeling-community. A web site is available where an individual can interact with the model and download a custom atlas. The URL is http://aurora.phys.utk.edu/(similar to)blass/ethyatl/

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.

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)

Absolute intensities in the ν7 band of ethylene: tunable laser measurements used to calibrate FTS broadband spectra

Abstract Three independent measurements of ν7 ethylene transitions at two different laboratories yield direct determinations of absolute intensity for 13 transitions. The 13 intensities are used to calibrate the intensities of a broadband high-resolution 10 μm spectrum of ethylene taken at the McMath Solar Telescope FTS facility. The least-squares fitting of the FTS intensity observations to the precisely determined TDL intensities results in validation of the broadband data for which sample pressure and temperature were marginally known. This “calibration” of the FTS spectrum makes it possible to determine intensities of transitions in several bands in the 800–1100 cm−1 broadband FTS spectrum.

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)

The gas phase Raman band contours of 1,3,5-trifluorobenzene and the infrared and Raman band contours of 1,3,5-trifluorobenzene-d3

Abstract The gas phase infrared and Raman spectra of 1,3,5-trifluorobenzene- d 3 has been recorded. The gas phase Raman spectrum of 1,3,5-trifluorobenzene- h 3 has also been recorded. Computer simulations of the band contours of the degenerate vibrational modes have been used to determine the first-order Coriolis coupling constants for both molecules. The ζ z values were then compared with those evaluated from force field calculations.

A high-resolution study of the 14.4-μm infrared band of deuterofluoroform

Abstract The FT-IR spectrum of the ν3 parallel band of deuterofluoroform has been recorded at a resolution of 0.0045 cm−1. Nine independent spectral parameters were determined which reproduce some 650 observed wavenumbers with a standard error of 3 × 10−4 cm−1. The constants derived for the ν3 band are (in cm−1): ν0 = 694.2822(3); B0 = 0.3309321(9); B3 = 0.3302464(11); αB = 6.859(10) × 10−4; αC = 1.429 × 10−4; D3J = 3.168(3) × 10−7; D0J = 3.188(3) × 10−7; DJK3 = 4.766 × 10−7; DJK0 = 4.864 × 10−7; and DK0 − DK3 = 2 × 10−10.

Analysis of the high-resolution 5-μm spectra of the ν4(E) and 2ν2(A1) bands of 12CD3F

Abstract The infrared spectrum of the ν 4 ( E ) and 2 ν 2 ( A 1 ) bands of 12 CD 3 F have been recorded and deconvolved to ∼0.005 cm −1 resolution. More than 1890 transitions have been assigned to one of the 37 subbands (−18≤ K Δ K ≤+18) comprising the spectrum of the ν 4 band with a maximum assigned J value of 41. The weak 2 ν 2 ( A 1 ) band has never been reported in the infrared prior to this work. A total of 358 transitions in K ≤ 8 subbands have been assigned to the 2 ν 2 band. The two bands are members of the 24 interacting state complex of 12 CD 3 F spectra in the 5-μm region. The ν 4 and 2 ν 2 spectra are highly perturbed, exhibiting local and global resonances. Effective parameters of the two bands were obtained by fitting the data in a restricted manner leaving out the obviously perturbed transitions. The effective parameters, the identification of the different resonances affecting the bands, and estimates of some of the coupling constants are reported.

Ground state rotational constants of 13CD3F and 12CD3F

Abstract Ground state rotational parameters B0, D0J, and D0JK have been determined for 13CD3F. Spectra of 12CD3F taken independently in the same time period were also assigned and analyzed as a control on the 13CD3F determination. The study used data from most of the 5-μm absorption bands as observed using a 5-m Littrow spectrometer. The 13CD3F parameters recovered are: B 0 = 0.6708360(40) cm −1 , D J 0 = 1.1004(44) x 10 −6 cm −1 , D JK 0 = 7.292(42) x 10 −6 cm −1 where the quoted errors are 95% simultaneous confidence limits in the last digits quoted (approximately 3 standard deviations). The results are based on 412 nonzero weighted combination differences yielding a standard deviation of the regression equal to 0.00129 cm−1.

The high-resolution spectrum of the ν1 (A1) band of 12CD3F

Abstract The spectrum of the ν 1 ( A 1 ) band of 12 CD 3 F has been recorded with a resolution of 0.010 cm −1 and deconvolved to 0.005 cm −1 . Over 1050 transitions have been assigned with K ≤ 16 and J ≤ 42. The spectrum is highly perturbed, exhibiting avoided crossings in most of the observed sub-bands. The origin of most of the local and global resonances has been determined and the coupling constants estimated. Due to the complexity of the spectrum resulting from the 24 potential interacting states in the region, the assigned frequencies were fitted in a restricted manner ( K ≤ 3, J ≤ 15), to obtain the following effective constants for the band: ν 0 = 2090.8118(20) cm −1 , α A = 1.19743 × 10 −2 cm −1 , and α B = −1.8489 × 10 −3 cm −1 . From an unrestricted least-squares analysis, fixing the above parameters the βs ( D v x = D 0 x − β v x ) were calculated to be β J = 1.7776 × 10 −7 cm −1 , β JK = 8.3406 × 10 −7 cm −1 , and β K = −6.3829 × 10 −7 cm −1 . These constants serve as good starting parameters for the global analysis necessary to fully analyze the 5-μm region of the 12 CD 3 F spectrum.