LASER FREQUENCY-MODULATED SPECTROSCOPY OF A LASER-GUIDED PLASMA IN SODIUM VAPOR - LINE POSITIONS FOR NAH (A(1)SIGMA(-X-1-SIGMA(+)), NA (9-13D AND 11-14S), AND AR (5P-4S)())

Laser frequency-modulated (FM) spectroscopy has been used as an axial probe of a laser-guided electric discharge in sodium-argon vapor conta ined in an optically accessible metal heat pipe oven. Absorption measu rements in the region 23 106-23 881 cm(-1) provided accurate line posi tions (+/-<0.006 cm(-1)) for 141 transitions in the v' = 3-8 <--v '' = 0 and v' = 5-9 <-- v '' = 1 bands of NaH (A(1) Sigma(+) - X-1 Sigma()). In addition, 18 transitions of Na (3p to 9-13d and 11-14s) and 10 of argon (5p - 4s) were measured. Analysis of the spectrum indicates t hat perhaps all absorption signals are due to neutrals NaH, Na, and Ar and are observed via ''population'' modulation. (C) 1997 Academic Pre ss.