Robert L. Sams

High temperature, high resolution infrared spectral measurements on the HNC–HCN equilibrium system

Spectral measurements have been made on HNC in equilibrium with HCN at temperatures ranging from 900 to 1250 K. From measurements of absorption intensity vs temperature it is determined that the ground state of HNC is 10.3±1.1 kcal/mol (43.1±4.6 kJ/mol) above the ground state of HCN. High resolution data are given on the following vibrational transitions for HNC near 3650 cm−1: 1000–0000, 1110–0110, 1200–0200, and 1220–0220. Measurements near 2780 cm−1 are also given for the 1000–0000 and 1110–0110 transitions for DNC. Aside from the low bending force constant, these measurements show nothing unusual about the bending potential function.

The high resolution infrared spectrum of the 2ν2 + ν3 and ν1 + ν2 + ν3 bands of 14N16O2: Vibration and vibration-rotation constants of the electronic ground state of 14N16O2

Abstract The A -type bands, 2 ν 2 + ν 3 and ν 1 + ν 2 + ν 3 , with band centers at 3092 and 3638 cm −1 , respectively, of 14 N 16 O 2 have been measured with resolution of 0.03 cm −1 or better. Spectroscopic constants have been derived for the upper states of both bands. Infrared determined band constants have been combined with laser-excited resonance fluorescence data to obtain a set of vibration and vibration-rotation constants for the ground state of 14 N 16 O 2 .

Infrared determination of C0 for phosphine via perturbation‐allowed Δ |k − l|= ± 3 transitions in the 3ν2 band

The 3ν2(A1) and 4ν2−ν2(A1) infrared bands of PH3 have been measured with high resolution. In the ν2=3 state an interaction between the K and K±3 levels gives rise to perturbation allowed ΔK = 3 transitions through a weak high order interaction. Since only one component of the K = 3 levels is of the proper symmetry to interact with the K = 0 levels there is a splitting of the K = 3 levels. Also detectable is the splitting of the K = 3 levels of the ground vibrational state. The measurements have been combined with microwave measurements to give accurate values for the ground state rotational constants B0, C0, D0J, D0JK, D0K, H0J, H0JJK, and H0JKK. The absence of observable inversion effects sets an upper limit of about 0.02 cm−1 for the inversion splitting of the 4ν2 level.

Removing aperture-induced artifacts from fourier transform infrared intensity values

Two Fourier transform infrared intensity artifacts have been observed at moderately high (0.1 cm(-1)) spectral resolution: Light reflected off the aperture was double modulated by the interferometer, producing a 2f alias, and the warm (approximately 310 K) annulus of the aperture seen by a cooled detector resulted in distorted line shapes and anomalous intensities in the fingerprint region. Although the second artifact has been alluded to previously, we report corrections to remove both of these anomalies and to demonstrate the efficacy of these corrections. Prior to correction, integrated-band intensities were found to be in error by up to 12%.

Infrared measurements on arsine: ν1 and ν3 bands, perturbation-allowed transitions, equilibrium structure

Abstract High resolution infrared measurements are reported on arsine (AsH 3 ) from 2260 to 1960 cm −1 . Numerous perturbation-allowed transitions have been found and are used to determine the C 0 rotational constant. Ten ground state rotational constants are determined including one that describes the splitting of the k = 3 levels. A complete equilibrium structure is determined. A total of 26 upper state constants are determined by means of a computer program which simultaneously fits both ν 1 and ν 3 bands and includes many off-diagonal matrix elements. This analysis will fit transitions through J = K = 12 to within experimental error, but it is concluded that to fit higher rotational transitions the perturbing effects of 2 ν 4 must be taken into account explicitly.

Infrared band strengths for methyl chloride in the regions of atmospheric interest

Abstract The infrared band strengths of seven vibrational band systems of methyl chloride between 3 and 17 μm were measured at 296 ± 1 K using a Fourier transform infrared (FT-IR) spectrometer. These results were obtained at maximum instrumental resolution of 0.06 cm −1 . The results should be of interest to atmospheric scientists, since methyl chloride may contribute measurably to the global greenhouse effect of the atmosphere.

The high resolution infrared spectrum of the ν1 band of HOCl

Abstract The ν1 bands of HO35Cl and HO37Cl have been recorded. Both the A- and B-type rotational transitions of these hybrid bands have been completely assigned, and spectroscopic constants have been obtained for both the ground and upper state. The ratio of the electric dipole moment derivatives ( ∂μ a ∂Q 1 ) ( ∂μ b ∂Q 1 has been found to be 0.985 ± 0.05 for ν1.

High-resolution infrared spectrum of the 859- and 1711-cm−1 bands of carbonyl sulfide (OCS)

Abstract The ν 1 and 2 ν 1 bands of OCS have been measured using grating spectrometers and a tunable diode laser spectrometer. Preliminary wavenumbers for OCS absorption lines useful for calibrating tunable laser systems are given for the wavenumber intervals 825 to 885 cm −1 and 1665 to 1737 cm −1 . Measurements and an analysis are given for the bands 10 0 0-00 0 0, 11 1 0-01 1 0, 20 0 0-00 0 0, 21 1 0-01 1 0, and 30 0 0-10 0 0 of the 16 O 12 C 32 S isotopic species and for the 20 0 0-00 0 0 band of the 16 O 13 C 32 S and 16 O 12 C 34 S species. Effective band constants are given for these bands.

HCN rotational-vibrational energy levels and intensity anomalies determined from infrared measurements☆☆☆★

Abstract New measurements have been made on the infrared transitions 1110-0000, 0400-0000, 1200-0110, 1220-0110, 0510-0110, 1330-0220, 1310-0200, 1220-0000, and 2000-0000 for HCN and on the 1110-0000 transitions for both H13C14N and H12C15N. Wherever possible those measurements were combined with laser measurements to obtain the best set of constants for describing the energy levels. Unusual intensity distributions were observed and attributed to intensity mixing through l-type resonance. Several P-branch lines of a Δ-Σ (1220-0000) transition were also observed although the intensity was somewhat less than predicted from l-type resonance effects.

Application of tunable diode laser absorption for trace stratospheric measurements of HCl: laboratory results

In this paper we report the results of a laboratory study for detecting the important atmospheric molecule HCl using a tunable diode laser coupled to a multipass White cell. In contrast to many such prototype studies, the calibration in this work was carried out near the concentration range of interest and verified using three different techniques. Employing a 40-m path length, we have demonstrated a detection limit (SNR = 1) in the 150–230 parts-per-trillion range at pressures around 9 Torr.