Vibrational Predissociation Dynamics of He−I₂(B) Mediated by Orbiting Resonances

Abstract

The He-I(2)(B, v) resonances embedded in the continuum of the v = 60 and 59 vibrational manifolds are investigated. Such states manifest a nature of overlapping and long-lived orbiting resonances, which are supported by centrifugal barriers originated in internal rotational excitation of I(2) and He within the complex. The same number of orbiting resonances, six, is found for v = 60 and for v = 59, with similar energy positions and wave functions, indicating that the spectrum of orbiting resonances changes slowly with the vibrational state v. Three of the orbiting resonances appear at nearly the same energies as the peaks observed experimentally in the vibrational relaxation cross section of I(2)(B, v = 21) through low temperature collisions with He. Such finding suggests that the cross section peaks have their origin in orbiting resonances of the He-I(2)(B, v = 21) complex formed upon the collision.

The role of orbiting resonances in the vibrational relaxation of I2(B,v′ = 21) by collisions with He at very low energies: a theoretical and experimental study

“…Similar spectra composed of several orbiting resonances were found for both v = 59 and 60. 43 Interestingly, the positions of three of the orbiting resonances found nearly coincided with the energy positions of the cross section peaks observed experimentally. 30 Although the spectrum of vdW resonances in a triatomic complex typically changes slowly with increasing vibrational state v, the states v = 59 and 60 are rather far from the v = 21 state of I 2 (B)ÀHe probed experimentally.…”

“…This result was also found in previous studies of orbiting resonances in vdW complexes. 40,41,43 Partial cross sections s v 0 j 0 ,v 0 (E) for the inelastic process (3) which involves tunneling through the centrifugal barrier associated with the Dv 0 = 0 channel are shown in Fig. 2.…”

“…36 The signature of orbiting resonances has been also found theoretically for complexes like Br 2 -Ne 32,37-41 and I 2 -He. 42,43 In the theoretical work of ref. 43 the possible existence of orbiting resonances in the I 2 (B,v = 59,60) À He vdW complex was investigated.…”

“…42,43 In the theoretical work of ref. 43 the possible existence of orbiting resonances in the I 2 (B,v = 59,60) À He vdW complex was investigated. The approach used was to simulate the vibrational predissociation of the I 2 (B,v 0 ) À He complex initially excited to the ground vdW resonance of the v 0 = v + 1 vibrational manifold which, for v = 59 and 60, is located at an energy close to those of the orbiting resonances of the v manifold (as one gets far away from v = 59 and 60, below or above, the coincidence in energy between the v 0 ground resonance and the v orbiting resonances rapidly vanishes due to the anharmonicity of the I-I interaction potential).…”

Effect of the Intermolecular Excitation in the Vibrational Predissociation Dynamics of van der Waals Complexes and the Implications for Control

“…The spectroscopy and photodissociation dynamics of van der Waals (vdW) clusters composed by molecules weakly bound to rare-gas atoms have been extensively studied during the last three decades. − Among the reasons for this research interest are that vdW complexes are prototypical systems to investigate intermolecular forces, intramolecular vibrational redistribution (IVR) mechanisms, unimolecular dissociation, and processes mediated by resonance states such as decomposition through predissociative decay. An extensive body of both experimental and theoretical information has been generated on these systems, which are generally well understood at present.…”