The effect of diatom-diatom collisions on depolarized light scattering linewidths

On the Kinetic Theory of the Enskog Fluid. Viscosity and Viscoelasticity, Heat Conduction and Thermal Pressure

“…spin diffusion and relaxation [11 -15], the influence of external magnetic and electric fields on the transport coefficients [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] (Senftleben-Beenakker effects [32][33][34]), flow bire fringence [35][36][37][38][39], broadening of spectral lines, in particular depolarized Rayleigh [36. 40] and rota tional Raman lines [41,42], A number of new effects has been discovered in rarefied polyatomic gases, e. g. the thermomagnetic torque [43] and the thermomagnetic force [44], the thermomagnetic pressure difference [45], the viscomagnetic heat flux [46] and diffusion flux [47] as well as heat flow birefringence [48] and diffusio birefringence [49].…”

Time resolved dynamics of phonons and rotons in solid parahydrogen

“…The calculated total cross section of s = 2.4 Å 2 for pH 2 -pH 2 collisions at 25 K agrees with the van den Hout experiment and shows that s actually increases from 0.38 to 0.80 to 2.4 Å 2 in going from 293 K to 77.8 K to 25 K. These calculations also indicate that increases in the contribution from s res largely account for these changes. 37 We speculate therefore that the derived collision cross section based on the T 2 measurements reflects s res and originates from EQQ interactions. The measured cross section of 2.08(10) Å 2 corresponds to a separation d = 0.9 Å of the interaction partners.…”

“…to convert the fitted T 2 value into an effective collision cross section (s) for identical particles with mass m and at a pressure P. This yields a value for s = 2.08(10) Å 37 similarly predict s(25 K) = 2.4 Å 2 . Given that the fast H 2 rotational dynamics is just at the limit of the temporal widths of the pump and probe pulses causing significant damping of the OKE signals, this level of agreement between our results and the earlier experiment and theory is highly satisfactory.…”

“…A theoretical treatment of the S 0 (0) cross section given by Coombe and Ko ¨hler in 1980 shows that the cross sections are strongly temperature dependent. 37 At low temperature, the collision time is increased and elastic collisions governed by the long-range EQQ interaction become dominant. The calculated total cross section of s = 2.4 Å 2 for pH 2 -pH 2 collisions at 25 K agrees with the van den Hout experiment and shows that s actually increases from 0.38 to 0.80 to 2.4 Å 2 in going from 293 K to 77.8 K to 25 K. These calculations also indicate that increases in the contribution from s res largely account for these changes.…”