Cross sections for rotational relaxation in alkali dimer molecular beams

✍ Scribed by E.L. Knuth; H.-G. Rubahn

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 310 KB
• Volume: 213
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(93)85409-h

✦ Synopsis

A sudden-freeze model for the extraction of effective rotational relaxation cross sections from nozzle beam expansions is refined by introducing a temperature-dependent cross section u,~( T). Since (i) u,,ccexp( -A&), (ii) the rotational energy level spacing AE,ccJand (iii) J*ccT"*itisassumedthatu,,(T)aexp[-or(7'/8,)'~*].H ere, J* stands for the most probable value of J and &=B/k, where B is the rotational constant. The value of (Y was determined from a semi-logarithmic plot of directly measured values of u,,,,( J) versus (T/e.) 'I'. The resulting sudden-freeze-model expression for uti,( r,,) was used to deduce values of a,,,, for Li/Liz and Na/Nal from measurements in nozzle-beam expansions. A combined plot of the directly measured values of u,,(J) and the deduced values of u& T,,) exhibits a common semi-logarithmic dependence on J*. Rotational relaxation cross sections deduced from quasiclassical trajectory calculations for Na/Li, (J= 5, J= 20) collisions at .?& = 100 meV agree quantitatively with the predicted values.