ELECTRICAL FIELD INDUCED PREDISSOCIATION IN MOLECULAR IODINE

Abstract

This work reports the observation of an electric field induced predissociation of the B-state of iodine. An argon-laser-pumped c.w. dye laser was used to excite a specific vibrational level ($v^{\prime}$) in the B-state. The predissociation rate was related to the modulation of the resulting fluorescence intensity by an applied electric field. The predissociation rate was determined for the levels $v^{\prime} = 4$ to $v^{\prime} = 20$, working in a Nearly collision-free regime, with fields of the order of $1\times 10^{4}$ v/cm. Under these conditions the maximum rate was $5\times 10^{2}$ per second. The predissociation was interpreted to be due to field-induced mixing between the bound B-state and a repulsive state via an electric dipole operator. From symmetry considerations this repulsive state must be either a $0^{+}_{g}$ or $1_{g}$ (in Hund’s case notation). Variation of the rate with $v^{\prime}$ indicates that the crossing occurs between $v^{\prime} = 3$ and 4 on the outer limb of the B-state potential. Writing the rate in terms of Fermi’s ``Golden Rule’’ and using calculated Franck-Condon factors, the transition dipole was estimated to be $1.3 \times 10^{-2}$ debye. The results support the predictions of $Mulliken^{1}$ and recent calculations of $Jaffe^{2}$.