MARK D. MARSHALL, Department of Chemistry-2243, Amherst College, P.O. Box 5000, Amherst, MA 01002-5000; KAMIL CAN IZGI AND J. S. MUENTER, Department of Chemistry, University of Rochester, Rochester, NY 14627.
Infrared laser-microwave double resonance spectroscopy is used to observe the Stark effect of tunneling transitions within the 1 and 3 hydrogen stretching states of \chemNH3. Dipole moments for 11 J,K states of 1 and 3 J,K states of 3 are measured to high accuracy. These data, combined with previous measurements in the ground and excited bending states, give a dipole moment function of: µ_v1 v2 v3 v4 = 1.5610 + 7.2 × 10-3 (v1 + \textstyle1 \over 2 ) - 2.271 × 10-1 (v2 + \textstyle1 \over 2 ) + 3.75 × 10-2 (v3 + 1 ) - 1.65 × 10-2 (v4 + 1 ) . µe = 1.561 D is the first experimental measurement of the \chemNH3 equilibrium moment. These results are also used to analyze and recalculate the dipole moment measured by Shimizu and coworkers in a vNH = 5 excited state of \chemNH3.