VIBRATIONAL-RELAXATION STUDY OF O-3 IN RARE-GAS AND NITROGEN MATRICESBY TIME-RESOLVED INFRARED-INFRARED DOUBLE-RESONANCE SPECTROSCOPY

A time resolved infrared-infrared double resonance technique is used t o study the vibrational relaxation of O-3 in rare gas and nitrogen mat rices. A tunable infrared (IR) pulsed source excites the nu(1) + nu(3) level of O-3 in the ground electronic state. A continuous wave (cw) C O2 laser probes the populations of the fundamental and upsilon(2)=1 le vels as a function of time. After minimization of thermal effects, the relaxation signal can be analyzed. At fixed probe frequency, the beha vior of the rise time of the signals with the pump frequency shows spe ctral diffusion to occur inside the inhomogeneous profiles. At high co ncentration in argon (O-3/Ar=1/250), intermolecular energy transfer is observed between the two sites. In xenon matrices, it has time to tak e place at concentrations 1/2000. The relaxation rates of the upsilon( 2)=1 level to the ground state are measured at different concentration s in rare gas and nitrogen matrices. At high dilution, a maximum relax ation time, called intrinsic relaxation time tau(i), is determined in the different matrices: it covers three orders of magnitude, from a fe w hundred nanoseconds in neon to 320 microseconds in xenon. The result s are discussed and compared with literature data within the frame of the isolated binary collision model. (C) 1998 American Institute of Ph ysics. [S0021-9606(98)01520-7].