The photodissociation cage effect in van der Waals complexes: Fluorescence spectra of I2 B(3Π0+u) from the hindered photodissociation of I2Ar at 488 nm

Abstract

The B→X fluorescence from I₂ produced in the hindered photodissociation of I₂Ar at 488 nm has been resolved. The spectra show several vibrational progressions with low rotational energy, the most prominent of these is a (v′,0) progression extending from v′ = 49 to at least v′ = 23. The I₂Ar complexes were excited and the I₂ fluorescence was observed under collision‐free conditions in a supersonic free‐jet expansion. We attribute these observation to one‐atom photodissociation cage effect in the I₂Ar comples, in which the molecular iodine, although excited more than 400 cm⁻¹ above B state dissociation limit, is prevented from dissociating by energy transfer to the argon atom, resulting in the breaking of the van der Waals bond: I₂Ar→I₂(B)+Ar, leaving the iodine molecule in a bound level of the B electronic state, 386–1889 cm⁻¹ below the dissociation limit. (AIP)