We report the results of an optical-optical double resonance experiment to determine the NaK (3 1PI) state potential energy curve. In the first step, a narrow band cw laser (PUMP) is tuned to line center of a particular 2(A) (1 SIGMA+)(v?, J?) <-- 1(X) (1 SIGMA+)(v?, J?) transition, and its frequency is then fixed. A second narrow band tunable cw Ti-Sapphire laser (PROBE) is then scanned, while (3 1PI) --> 1(X) (1 SIGMA+) violet fluorescence is monitored. The Doppler-free signals accurately map the (3 1PI) (v, J) ro-vibrational energy levels. These energy levels are then fit to a Dunham expansion to provide a set of molecular constants. The Dunham constants, in turn, are used to construct an RKR potential curve. Resolved (3 1PI) (v, J) --> 1(X) (1 SIGMA+) (v?, J?) fluorescence scans are also recorded with both PUMP and PROBE laser frequencies fixed. Comparison between observed and calculated Franck-Condon factors is used to determine the absolute vibrational numbering of the (3 1PI) state levels and to determine the variation of the (3 1PI) --> 1(X) (1 SIGMA+) transition-dipole moment with internuclear separation. The recent theoretical calculation of the NaK (3 1PI) state potential reported by Magnier and Milli? (1996, Phys. Rev. A 54, 204) is in excellent agreement with the present experimental RKR curve.
Citation: Journal of Molecular Spectroscopy
Volume: 193 (2)
Pub Type: Journals
Molecular spectroscopy, Optical physics