Perturbation-facilitated optical-optical double resonance spectroscopy of the h0u−(3P1) and H1u(3P1) ion-pair states of I2

Abstract

Perturbation-facilitated optical-optical double resonance spectroscopy has been applied to study the h0u−(3P1) and H1u(3P1) ion-pair states of I2 correlating with I−(1S)+I+(3P1). The intermediate states used were the g/u parity mixed states found in the B 3∏(0u+)−X 1∑g+ absorption spectrum near the dissociation limit. We identified several B 3∏(0u+)∼3∏(0g−) coupled states by hyperfine interactions for the first time. These states had the 0u+ and 0g− double-faced character and facilitated to combine the X 1∑g+ ground state with the h0u−(3P1) state in the (1+1) photon excitation scheme following the optical selection rules for one-photon transition. We also accessed the H1u(3P1) state through the B 3∏(0u+)∼c1g mixed state, and elucidated the heterogeneous coupling between the h0u−(3P1) and H1u(3P1) states. Our analyses covered the region of about 48 200 to 50 300 cm−1, and gave the molecular parameters of the h0u−(3P1) state valid for v=0–17 and those of the H1u(3P1) state for v=0–20. The Π3(0g−) state used as an intermediate state was analyzed through the dispersed h0u−(3P1)−3∏(0g−) emission in conjunction with the Franck–Condon factor calculations, and the principle spectroscopic constants of the Π3(0g−) state were reported.