Chemical Physics Letters, Vol.429, No.1-3, 27-31, 2006
Direct evidences of scattering resonances enhancement in the vibrational relaxation of I-2 (B-3 Pi(+)(0u), v'=21) by collisions with He at very low temperatures
The vibrational deactivation of I-2(B, v' = 21) by He in the low energy regime, was studied under single collision conditions, in a super-sonic expansion. The time resolved fluorescence signal (TRFS) from the (B; v' = 21)->(X; v" = 1) transition was collected at several distances from the nozzle to access different local temperatures in the range (0.17-6) K. From the analysis of the TRFS the value of the relaxation cross-section was extracted and it showed to decrease with energy through a series of peaks. This experimental observation, confirms the role of scattering (mainly orbiting) resonances as theoretically postulated previously. (c) 2006 Elsevier B.V. All rights reserved.