NEAR-INFRARED DIODE-LASER SPECTROSCOPY OF THE NITROGEN MOLECULE IN RYDBERG STATES

Two electronic bands of the nitrogen molecule were observed by near-infrared diode laser absorption spectroscopy around the 1.3-mu-m region. One band was assigned to the transition from the E 3-SIGMA-g+ (upsilon" = 0) to D 3-SIGMA-u+ (upsilon' = 0) state. Both states were previously assigned as Rydberg states with an s- or p-electron, and an N2+ X 2-SIGMA-g+ core. Fine structure constants of these states were determined for the first time. The second band looked as if it belonged to a doublet system of the molecular ion, but it turned out to be that of the neutral when the doublet structure was resolved into triplet components by means of sub-Doppler saturation spectroscopy. This band was also assigned as a 3-SIGMA+ - 3-SIGMA+ transition and was tentatively assigned to a vibrational hot band of the D-E transition based on the rotational constants, lifetime, transition dipole moment, and systematic line broadening due to predissociation.