ABSORPTION CROSS SECTION OF GASEOUS ACETYLENE AT 85 K IN THE WAVELENGTH RANGE 110-155 nm

Abstract

Absorption spectra and absorption cross sections of gaseous acetylene, C 2 H 2 , at 298 and 85 K were measured in the wavelength range 110-155 nm with a slit-jet system coupled to a synchrotron as a source of vacuum ultraviolet light. Using published spectral parameters of C 2 H 2 , we simulated the absorption profile for the Rydberg transition to state 4R 0 in the range 124.6-125.1 nm, according to which the temperature of the jet-expanded sample at stagnation pressure 200 Torr is 85 ± 5 K. Our cross sections of C 2 H 2 are applicable for determining properties sensitive to temperature for diagnostic work on Saturn and Titan.

Infrared and Ultraviolet Spectra of Diborane(6): B2H6 and B2D6

“…These fitted components appear also in Figure ; Figure S1 (Supporting Information) shows the relative residuals to the fit of the spectrum for gaseous B 2 H 6 , which indicates the necessity for all 11 components and the quality of the fit. The experimental oscillator strengths are calculated with this formula , in which the unit of σ is Mb (= 10 –22 m 2 ) and of ν is cm –1 . The results of this deconvolution are presented in Table ; as the data therein are transcribed directly from the output of the fit, they exhibit insignificant digits but are left without rounding to retain the sense of the fit.…”

“…The appearance of many lines interpreted as combinations of modes active in absorption and scattering, however, enables estimates of the participating Raman modes. Although the nuclear arrangement of 10 B 11 BH 6 according to point group C 2v is not centrosymmetric, such that of 18 modes all but 2 of symmetry class A 2 , ν 8 and ν 9 , are formally active in infrared spectra, the dissimilarity with 11 B 2 H 6 is weak; few of the additional modes might have intensity comparable with the 8 modes of the latter, consistent with our calculations. Our analysis of our newly recorded spectra is assisted by the reported spectra of diborane in both gaseous and crystalline phases for both B 2 H 6 and B 2 D 6 in natural abundance and 10 B enriched to 96%; 2 these conditions were favorable for the observation of most bands or lines in the active infrared modes in the three species for B with either H or D. As many lines in absorption by B 2 H 6 or B 2 D 6 dispersed in solid neon have widths comparable with the maximum spectral resolution practicable for our recording of these spectra, a saturation of absorption causes distortion of lines and inaccurate ratios of their statures (net maximum absorbance relative to a baseline); for this reason the apparent ratios of those intensities differ from the formal ratio of relative abundances, but the trends are clear.…”

“…The infrared spectra of gaseous and crystalline diborane have been reported in detail, 2 which led to an empirically derived harmonic or quadratic force field, 3 but the published ultraviolet spectra of diborane have poor quality resulting from the primitive conditions of their measurements before year 1950. 4,5 For a sample of diborane that contains boron in natural abundance with two stable isotopic variants, 0.801 11 B and 0.199 10 B, the effective ratio of relative abundance of species 11 B 2 H 6 / 10 B 11 BH 6 / 10 B 2 H 6 is hence about 16:8:1. For diborane dispersed in solid neon at 4 K, the infrared spectral lines are narrow and well resolved, allowing accurate measures of the isotopic shifts from the dominant species, 11 B 2 H 6 , to the isotopic variants 10 B 2 H 6 and 11 B 10 BH 6 .…”

Vacuum-UV spectroscopy of interstellar ice analogs

“…The National Synchrotron Radiation Research Center (NSRRC) in Taiwan (Lu et al 2005;Cheng et al 2011;and Wu et al 2012), ASTRID at the University of Aarhus, and the UK Daresbury Synchrotron Radiation Source (Mason et al 2006) were used as VUV sources in their measurements. This requires application for synchrotron beamtime, leading to a limited use, and one needs to work with a transportable chamber.…”

Vacuum-Ultraviolet Absorption Spectra of Icy C2H4 at 13–60 K

“…The thermal spectral responses of condensed and gaseous molecules might thus differ with or without the interaction of adjacent molecules. The thermal variation of absorption for a molecule in the gaseous phase (Lu et al, 2010;Cheng et al, 2011) is generally greater than that in a condensed state; for the thermal effect on spectra, attention has been devoted much to the gaseous molecule and little to condensed molecules. For this reason, an investigation of the thermal absorption for molecules in condensed phases is lacking, and needs to be established.…”