High-resolution laser spectroscopy and magnetic effect of the $\tilde B$B̃2E′ ← $\tilde X$X̃2A2′ transition of 14NO3 radical

Rotationally resolved high-resolution fluorescence excitation spectra of 14NO3 radical have been observed for the 662 nm band, which is assigned as the 0–0 band of the $\tilde B$B̃2E′ ←$\tilde X$X̃2A2′ transition, by crossing a single-mode laser beam perpendicularly to a collimated molecular beam. More than 3000 rotational lines were detected in 15 070–15 145 cm−1 region, but it is difficult to find the rotational line series. Remarkable rotational line pairs, whose interval is about 0.0246 cm−1, were found in the observed spectrum. This interval is the same amount with the spin-rotation splitting of the $\tilde X$X̃2A2′ (υ = 0, k = 0, N = 1) level. From this interval and the observed Zeeman splitting up to 360 G, seven line pairs were assigned as the transitions to the 2E′3/2 (J′ = 1.5) levels and 15 line pairs were assigned as the transitions to the 2E′1/2 (J′ = 0.5) levels. From the rotational analysis, we recognized that the 2E′ state splits into 2E′3/2 and 2E′1/2 by the spin-orbit interaction and the effective spin-orbit interaction constant was roughly estimated as –21 cm−1. From the number of the rotational line pairs, we concluded that the complicated rotational structure of this 662 nm band of 14NO3 mainly owes to the vibronic interaction between the $\tilde B$B̃2E′ state and the dark $\tilde A$Ã2E″ state through the a2″ symmetry vibrational mode.