Electronic and vibrational predissociation in ArI2 photodissociation dynamics

Abstract

Quantum dynamical calculations on the photodissociation process: ArI2(X)+hν→Ar+I2(B) or Ar+I+I have been performed using diatomics-in-molecule semiempirical potential energy surfaces in the spectral region of the I2(B,v=15–25)←I2(X,v=0) transition. The B state responsible for vibrational predissociation producing Ar+I2(B) is coupled to four dissociative states inducing electronic predissociation to Ar+I(2P3/2)+I(2P3/2). These dissociative states correlate to the a(1g), a′(0g+), B″(1u), 1(2g) electronic states of I2. Both linear and perpendicular initial ArI2(X) isomers are considered. For the linear isomer, only the a′ state has non-negligible effect on photodissociation dynamics, although total photon absorption cross sections are not significantly modified when coupling to a′ is taken into account, partial cross sections corresponding to vibrational predissociation are smaller. For the perpendicular isomer, resonance decay rates are increased, mainly by the coupling to a′(0g+), 1(2g), and a(1g) states. Decay rates oscillate as a function of the vibrational excitation of I2(B) but the main source of oscillation is the intramolecular vibrational energy redistribution which occurs in vibrational predissociation, rather than Franck–Condon oscillations in electronic predissociation.