IR-Microwave Double Resonance Studies of Tunneling Frequencies in the nu1 and nu3 States of Ammonia.

Infrared laser-microwave double resonance spectroscopy has been used to observe tunneling transitions in the nu1 and nu3 hydrogen stretching states of NH3 . Inversion frequencies in 15 rotational states of nu1 and 6 rotational states of nu3 were measured to accuracies of ±25 kHz. Comparisons between ground state and v 1 = 1 data indicate that x-y Coriolis interactions are responsible for much of the angular momentum dependence of the nu1 inversion splittings. The J ,K rotational quantum number dependence for tunneling in nu3 is very different from that in either the ground state or nu1 .