The complex H 3N-SO 3⋯H 2O is observed by pulsed nozzle Fourier transform microwave spectroscopy using a newly designed concentric, dual-injection nozzle source. This source allows two reactive species to be injected independently into a seeded supersonic expansion by introducing gases through a pair of concentric hypodermic needles situated downstream of the nozzle orifice. Microwave spectra of the parent form of H 3N-SO 3⋯H 2O, as well as nine isotopically substituted derivatives are observed, and the N-S bond length is estimated to be 1.83(13) Å. This value is in reasonable agreement with previous theoretical calculations and suggests that the complexation of H 3N-SO 3 with water produces a substantial contraction of the nitrogen-sulfur bond. The spectrum shows no evidence of internal motion of the water subunit.
Bibliographical noteFunding Information:
This work was supported by the National Science Foundation, the donors of the Petroleum Research Fund, administered by the American Chemical Society, and the Minnesota Supercomputing Institute. We are also grateful to Professor Fu-Ming Tao for making the results of  available to us prior to publication.
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