Measurements of inelastic cross sections for the (j,m) = (2,0)→(3,0) rotational transition of CsF in collisions with atoms and molecules

✍ Scribed by U. Borkenhagen; H. Malthan; J.P. Toennies

• Publisher: Elsevier Science
• Year: 1976
• Tongue: English
• Weight: 296 KB
• Volume: 41
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(76)80796-8

✦ Synopsis

Individual state-?-to-state rotational transitions have been resolved in small angle scattering of po!arized CsF molecules on Ne, Ar, Cz Hg. Nz. CO, COz. CHFS at center of mass energies of about 0.1 eV. The absolute inelastic cross sections range from 5 A up to 600 A2 _ Most cf our knowledge oi inelastic collision processes comes from bulk rate studies [I]. Recently the use of lasers has made it possible to measure rate constants for specified quantum states [2] _ Considerably more information on *he elementary collision process is obtained in a scattering experiment. Both rotational and vibrational quantum excitation have been resolved in i&n-molecule collisions over a wide range of energies and angles (for a review see ref. [3]). For neutral partners only two (in comparison primitive) quantum resolved experiments are available [4-61.

In this letter we report on recent results* from the state selection method used in one of these previous studies.

In the new apparatus CsF moiecules, which have been rotationally cooled to 6 K [8] by expansion in an Xe-seeded beam from the oven temperature of 8OCi K, are first velocity selected (6% fwhm) and then passed through an eIectrostatic quadrupole field, which focuses Only moIecu:es in the (ii$mi) = (2,0) or (3,oj initial state into the scattering region. The target beam is a skimmed nozzle beam with an angular divergence of 4" (fwhm), which is admitted perpendicular to the primary beam. A hombgenedus electric field E at right angles to bothbeams prevents randomization of the m-states and provides-for orientation of the CsF molecule. Since E is perpendicular to both v1 and v2 the * A preliminary presentation of these results is contained in ref.

PI.