Temperature dependence in the multiphoton dissociation of 32SF6

Abstract

The multiphoton dissociation of 32SF6 at 10.59 μm has been studied as a function of the temperature between 223 and 413 K. The observed decrease of the reaction yield with increasing temperature varies strongly with the laser energy fluence at the applied conditions. Rate constants for the unimolecular decomposition of sulfur hexafluoride induced by the monochromatic infrared radiation are derived at 223, 293, and 343 K.

A model study of the influence of the properties of the quasicontinuum on MPA and MPD spectra of SF6at different rotational temperatures

“…Figures 4(a) and ( 6) show MPD spectra at I = 8 x IO' W cm-2 corresponding to MPA spectra in figures 2(b) and 3. Contrary to the experimental observations (Duperrex andVan den Bergh 1979, Del Bello et al 1986), the MPD yield does not decrease around the peak with increasing temperature. The temperature dependence in the long wavelength wing is, however, similar to the experimental observation.…”

“…However, the thermal dependences of MPA and MPD around the peak of the spectrum (which occurs between 944-949 cm-') do not show similar behaviour. While absorption at low Auence in all cases increases around the peak with increasing cell/rotational and vibrational temperature, dissociation shows a decrease around the peak in both cell and molecular beam studies (Tsay et a1 1979, Boschetti et a1 1984, Duperrex and Van den Bergh 1979, Del Bello et a1 1987. Although it is not clear whether the decrease is due to the increase in rotational and/or vibrational temperature, the study of Schulz et al (1980) indicates that the M P D yield beyond 944 cm-' will decrease with increasing vibrational temperature.…”

“…Again, the general agreement is that the first few excitation steps determine the temperature dependence of the spectra (Cantrell et al 1981), although the relative contributions of rotational and vibrational temperatures are not yet clear. The results of cell experiments (Tsay et a1 1979, Duperrex andVan den Bergh 1979) are now supplemented by molecular beam experiments where rotational and vibrational temperatures can be varied independently (Schulz et a1 1980, Boschetti et a1 1984. According to the nature of thermal variation, the MPA and MPD spectra can be divided into three distinct regions: (1) the long wavelength wing, (2) the region of maximum absorption and dissociation and (3) the high-frequency wing.…”

Master equations for photochemistry with intense infrared light (III) the influence of molecular parameters in URIMIR

“…Similarly we neglect here the complications which are due to the reducibility of the rate coefficient matrix (part I1 section 4.6). This arises from the broad thermal initial distribution of energies and angular momenta, and leads to sizeable temperature effects in URIMIR, which have already been observed experimentally [14]. However, this does not affect the trends to be discussed below.…”