Journal of Physical Chemistry A, Vol.117, No.50, 13535-13542, 2013
Spectroscopic Study of N-2(b(1)Pi(u), nu=8) by Atmospheric-Pressure Resonant-Enhanced Multiphoton Ionization and Fluorescence Detection
A spectroscopic analysis of the strongly perturbed N-2(b(1)Pi(u), nu = 8) state has been conducted, accounting for b(1)Pi(u)(nu = 8) <- X (1)Sigma(+)(g)(nu = 0) transitions, for the first time, up to J' = 20. A novel laser spectroscopy technique, using a combination of resonant-enhanced multiphoton ionization and fluorescence detection at atmospheric pressure, avoids the severe effects of perturbation reported in past extreme vacuum ultraviolet absorption experiments that produced weak and unusable spectra for the nu = 8 level. The R, Q and P branches of the three-photon absorption transition b(1)Pi(u)(nu = 8) <- X (1)Sigma(+)(g)(nu = 0) were fit, allowing rotational term energy assignment up to J' = 20 and molecular constants to be determined. Evidence of the previously suspected perturbation in b(1)Pi(u)(nu = 8) is clear in this data, with significant A-type doubling at higher J' along with an anomalous negative value determined for the centrifugal distortion coefficient.