Sub-Doppler studies of Rydberg states of ammonia using multiphoton excitation

The $\tilde B^1E''-\tilde X^1 A_1$ band systems of $NH_3$ and $ND_3$ were recorded using multiphoton ionization and their rotational structures were analyzed. The $2^3_0$ vibronic band of $ND_3$ was also recorded Doppler-free using the method of two-photon excitation with counterpropagating beams. Selected lines were examined in magnetic fields of up to 10.5 kG. Measurements of the Zeeman splittings for these lines yielded the electron orbital magnetic moment. The total internal angular momentum, deduced from the rotational analysis, was then analyzed into its separate electronic and vibrational components.