High-resolution laser spectroscopy and magnetic effect of the &Btilde;²E'←&Xtilde;²A2' transition of the 15N substituted nitrate radical.

Rotationally resolved high-resolution fluorescence excitation spectra of the 0-0 band of the &Btilde²E'←&Xtilde²A₂' transition of the ¹⁵N substituted nitrate radical were observed for the first time, by crossing a jet-cooled molecular beam and a single-mode dye laser beam at right angles. Several thousand rotational lines were detected in the 15080-15103 cm^-1 region. We observed the Zeeman splitting of intense lines up to 360 G in order to obtain secure rotational assignment. Two, nine, and seven rotational line pairs with 0.0248 cm^-1 spacing were assigned to the transitions from the &Xtilde²A₂' (υ = 0, k = 0, N = 1, J = 0.5 and 1.5) to the ²E'_3/2 (J' = 1.5), ²E'_1/2 (J' = 0.5), and ²E'_1/2 (J' = 1.5) levels, respectively, based on the ground state combination differences and the Zeeman splitting patterns. The observed spectrum was complicated due to the vibronic coupling between the bright &Btilde²E' (υ = 0) state and surrounding dark vibronic states. Some series of rotational lines other than those from the &Xtilde²A₂' (J = 0.5 and 1.5) levels were also assigned by the ground state combination differences and the observed Zeeman splitting. The rotational branch structures were identified, and the molecular constants of the &Btilde²E'_1/2 (υ = 0) state were estimated by a deperturbed analysis to be T 0 = 15098.20(4) cm^-1, B = 0.4282(7) cm^-1, and D_J = 4 × 10^-4 cm-1. In the observed region, both the ²E'_1/2 and ²E'_3/2 spin-orbit components were identified, and the spin-orbit interaction constant of the &Btilde²E' (υ = 0) state was estimated to be -12 cm^-1 as the lower limit. [ABSTRACT FROM AUTHOR]