title: Vibrational relaxation dynamics of I35Cl(B, v') induced by low-temperature collisions with He atoms.
abstract: Using laser-induced fluorescence and two-laser, pump-probe spectroscopy, collision-induced vibrational relaxation is observed to compete with the dissociation of electronically excited ICl in a helium carrier gas expansion. By thoroughly characterizing the expansion properties, we observe that collisions of ICl(B, v'= 3) molecules with He atoms in the expansion induce vibrational relaxation of the initially prepared dihalogen down to rotor states in the next lower ICl(B,v'= 2) level on timescales that compete with the rate for non-adiabatic transfer from the B state to the Z1 state. The resulting ICl(B,v'= 2,j') product rotational distribution, along with the analogous ICl(B,v'= 1,j') distribution formed by collisional relaxation of molecules in the long-lived ICl(B,v'= 2) level are compared to ICl(B,v'= 2,j') products formed by vibrational predissociation of He...ICl complexes prepared in different intermolecular vibrational levels within the He + ICl(B,v'= 3) potential. No evidence is observed for resonance-enhanced collisional cross sections, even at the low temperatures achieved, T < 1.0 K.
authors.affiliation: Department of Chemistry, Washington University, One Brookings Drive, CB 1134, Saint Louis, Missouri, 63130, USA.
authors.forename: Joshua P
authors.initials: JP
authors.lastname: Darr
authors.forename: Richard A
authors.initials: RA
authors.lastname: Loomis
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002713:Chlorine / Q000737:chemistry* / Q000378:metabolism; D003080:Cold Temperature; D006371:Helium / Q000737:chemistry*; D007455:Iodine / Q000737:chemistry* / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics
chemical_list: D006371:Helium; D002713:Chlorine; D007455:Iodine