VIBRATIONAL TO TRANSLATIONAL RELAXATION IN SF6–Ar MIXTURES: QUANTITATIVE ANALYSIS

Using lasers to measure pollutants

“…MP processes have been investigated using a number of techniques. In recent years it was widely accepted that the pulsed OA technique is a simple and powerful method to investigate many parameters relevant to MP absorption processes [52,53]. Here we give an outline of the pulsed OA technique [54,55] (Fig.…”

Global warming and SF6 molecule

“…Values of τ rot in the range of (1-2)×10 -7 s [23][24][25][26][27][28][29][30] show its ability to reach proper ro-vibrational state due to mutual collisions with its gas partners, enhancing the absorption ability more than 50 %. Values of τ V-T in the range of (2-5)×10 -6 s [19][20][21][22] show its ability to transfer absorbed energy from its vibrational to translational modes of its collisional partners efficiently. Recent measurements show that concentration of sulfur hexafluoride in atmosphere is 10 8 times less than concentration of more investigated main greenhouse gas CO 2 .…”

“…In some of these investigations, due to use of the high buffer-gas pressures and the high laser fluences, the authors have detected the average number of absorbed photons <n>, which has exceeded drastically S-F bound energy, i.e. <n> was bigger than 33 [16,18,20,22].…”

“…The main experimental parameter obtained and analyzed in this work is the total average number of absorbed photons <n> total for SF 6 molecule surrounded with Ar as a buffergas species. Equation, used to calculate <n> total values from the experimental PA parameters, valid for all types of gas mixtures, has a form [15][16][17][18][19][20][21][22] (…”

“…where β is the ratio of degeneracy of the upper and lower vibrational levels, τ p is laser pulse duration and τ is equilibration time of the absorber level and reservoir level, usually taken as rotational relaxation time in previous investigation [15,18,20]. This model is valid in three limiting cases: 1) weak coupling (collisionless), when (τ p / τ) < 1; 2) strong coupling (collisional) when (τ p / τ) > 1 and low flux ((σ 0 Φτ) / (f r f i τ p ) < 1); 3) strong coupling (collisional) when (τ p / τ) > 1 and high flux((σ 0 Φτ) / (f r f i τ p ) > 1).…”