HIGH RESOLUTION SPECTROSCOPY OF $NA_{3}$ BY CW RESONANT TWO-PHOTON IONIZATION

Author Institution: Dept. of Physics, The Pennsylvania State UniversityNa clusters are generated in a seeded supersonic molecular beam. $Na_{3}$ molecules are resonantly excited by a cw single mode dye laser and subsequently ionized by a cw Argon ion laser. The $Na_{3}^{+}$ signal is detected through a quadrupole mass spectrometer. In this way, spectra of the B-X transition of $Na_{3}$ around 620 nm were recorded with linewidths of 0.1 to 1. GHz. The rotational transitions exhibit different hyperfine splittings which are resolved for part of the lines. First results for the rotational constants from an analysis of the spectra with model Hamiltonians will be reported. In addition, we are setting up an optical-optical double resonance experiment in order to label several rotational transitions