Radiative and Collisional Transitions between Coupled Vibrational Modes of CO2

Abstract

Each of the two energy levels of CO2 at 1388 and 1285 cm−1 is an equal mixture of doubly excited bending mode and singly excited symmetric stretch mode. The collision numbers of these levels for CO 2–CO 2 collisions are calculated by using the mixed wavefunctions in conjunction with the SSH theory that has been expanded to include two-quantum transitions. This relaxation is shown to take place via various near resonant V-V processes at transition rates of the order of 10 4 sec −1 · torr−1. In particular, direct de-excitation of the lower laser level via singly excited bending mode is shown to be important. An explanation is given for transitions that involve a change of the vibrational angular momentum l, by Δ l = ± 2. Three independent experiments have measured rates in reasonable agreement with those calculated here Quite striking is the substantial disagreement between these three experiments on the one hand and the published interpretation of the Rhodes—Kelly—Javan (RKJ) experiment on the other. To resolve this discrepancy, the RKJ experiment is analyzed in detail, and a new interpretation is given that explains one of the observed transient effects as caused by stimulated two-photon processes and the other by rotational relaxation of the upper laser level.

Errors in Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) kinetic temperature caused by non‐local‐thermodynamic‐equilibrium model parameters

“…In an early experiment, Rhodes et al [1968] indicated a rate of relaxation of the 10 0 0 level in V‐V CO 2 exchange of 1.15 × 10 −11 cm 3 s −1 , although they pointed out that they could not distinguish if the 02 2 0 level was involved. Later interpretations of that experiment [ Seeber , 1971] proposed that the rate measured by Rhodes et al was more likely not related to our process 4. Additionally, Seeber calculated a rate for the 02 2 0 state relaxation leading to a combined relaxation rate of the 020 states of 1.6 × 10 −11 cm 3 s −1 .…”

Kinetic study of low-temperature CO2plasmas under non-equilibrium conditions. I. Relaxation of vibrational energy

“…Briefly, SSH assumes that strong, short-range, repulsive forces are effective in producing vibrational transitions. In practice, this theory leads to relatively simple expressions for the state-specific relaxation rates [39,40]. They are sometimes used for quantitative comparison with experimental determinations in the absence of any other better theoretical estimations, or, especially, for the scaling of the rate coefficients with quantum numbers over a very limited number of known coefficients.…”

“…In this work, apart from V-T and V-V, we have investigated the influence of spontaneous emission. Overall, these processes can be grouped into the following categories: Extended versions of the original SSH theory include two-quantum transitions (see [40] for more details).…”