Branching ratios and radiative lifetimes of the U, L, and i states of thorium oxide

The dispersed laser induced fluorescence resulting from excitation of the U(|Ω|=1)-X1Σ+(0,0), L(|Ω|=1)-X1Σ+(0,0), and I(|Ω|=1)-X1Σ+(0,0) bands near 398, 402, and 512 nm, respectively, of thorium oxide, ThO, has been recorded and analyzed. The branching ratios for the fluorescence decay from the U(|Ω|=1)(v=0), L(|Ω|=1)(v=0), and I(|Ω|=1)(v=0) states are determined. Radiative lifetimes of 57 ± 2, 17 ± 1, 115 ± 4, and 468 ± 30 ns for the U(|Ω|=1)(v=0), L(|Ω|=1)(v=0), I(|Ω|=1)(v=0), and C1Π1(v=0) states, respectively, were determined from the analysis of the fluorescence decay curves. Transition dipole moments for numerous bands involving the U(|Ω|=1)(v=0), L(|Ω|=1)(v=0), I(|Ω|=1)(v=0), and C1Π1(v=0) states are determined. Possible optical pumping and detection schemes are proposed for experiments using ThO to search for the electric dipole moment of the electron.