Abstract

We have completed a measurement of several EF ${}^1{\Sigma }_g^{+}$ levels in H₂ and its isotopomers with an absolute accuracy better than 1 part in 10^s. The EF ← X interval is measured by Doppler-free two-photon absorption with counterpropagating beams at 202 nm. To obtain high peak power with bandwidths that approach the Fourier-transform limit, the output of a single-mode cw ring dye laser operating near 606 nm is pulse amplified in a three-stage dye amplifier pumped by a seeded Nd:YAG laser. The required 202-nm light is generated by frequency tripling the 606-nm pulses. Transitions to the EF states are detected by resonant multiphoton ionization induced by the absorption of a third photon at 202 nm.

© 1995 Optical Society of America