Nonequilibrium Effects in Atomic Recombination Reactions

Abstract

12 The self-consistent-field (SCF) equations were solved for this open shell system by a method which has proved quite useful to the authors. Starting with a reasonable guess for the occupied SCF orbitals, natural orbital iterations are carried out on a CI wavefunction including all singly excited configurations which retain the open shell spin coupling of the SCF wavefunction. When the coefficients of all configurations but the first become vanishingly small, the first configuration is the SCF wavefunction within the chosen basis set. The general problem of extracting a Hartree-Fock wavefunction from a correlated wavefunction was discussed some time ago by N.Relaxation in the bromine-argon system is investigated by approximating the time evolution with a sequence of trajectory calculations. Two systems are considered: (a) recombination of bromine atoms via the radical-molecule complex mechanism and (b) rotational relaxation of a rigid rotator in a thermal bath. The phenomenological and equilibrium rate coefficients for recombination at 300 0 K are computed and compared. Nonequilibrium effects lead to a 19% discrepancy between the two rate coefficients after an initial transient period during which the phenomenological rate coefficient shows a distinct time dependence. Comparison of the rotational relaxation of Brl and the rigid rotator shows the importance of vibrational-rotational coupling for highly excited molecules. The relaxation time of the vibrationally excited molecules is much greater than that of the rigid rotators.

Trajectory study of atomic recombination reactions. VII. Recombination of I and Br atoms

“…Recombination of iodine and bromine atoms in inert gases has been studied previously (1)(2)(3)(4)(5)(6) using classical 3-D trajectory technique and Monte Carlo method of sampling. Two dynamical mechanisms were considered in these calculations: the classically bound, or radical-molecule, complex (BC) mechanism X M + X + X 2 + M 'Research sponsored, in part, by the Air Force Ofice of Scientific Research, Air Force Systems Command, USAF, under grant No.…”