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(|Omega| = 1) - X-1 Sigma(+)(0,0), L(|Omega| = 1) - X-1 Sigma(+)(0,0), and I (|Omega| = 1) - X-1 Sigma(+)(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(|Omega| = 1)(nu = 0), L(|Omega| = 1)(nu = 0), and I (|Omega| = 1)(nu = 0) states are determined. Radiative lifetimes of 57 +/- 2, 17 +/- 1, 115 +/- 4, and 468 +/- 30 ns for the U(|Omega| = 1)(nu = 0), L(|Omega| = 1)(nu = 0), I (|Omega| = 1)(nu = 0), and C-1 Pi(1)(nu = 0) states, respectively, were determined from the analysis of the fluorescence decay curves. Transition dipole moments for numerous bands involving the U(|Omega| = 1)(nu = 0), L(|Omega| = 1)(nu = 0), I (|Omega| = 1)(nu = 0), and C-1 Pi(1)(nu = 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.