Spectroscopic study on the iodine molecule by a sequential three-photon excitation

Abstract

A three-photon absorption technique which utilizes a visible B 3Π0+u−X 1Σ+g transition followed by a simultaneous two-photon absorption was applied to study an ion-pair state of molecular iodine. The derived molecular parameters were Te=51 707 cm−1, ωe=131 cm−1, and Be=0.021 90 cm−1 for the F′(0+u) ion-pair state, which dissociates to I−(1S)+I+(1D). The excitation of I2 to a single rovibronic level of the F′ state was achieved and its fluorescence spectrum showed two discrete band systems corresponding to the transitions to: (1) the ground state at higher vibrational levels; and (2) the weakly bound state (Te=19 286 cm−1, ωe=64 cm−1, and re=3.65 Å) converging to the I(2P3/2)+I(2P1/2) products.