The H2s Dimer Is Hydrogen-Bonded: Direct Confirmation From Microwave Spectroscopy

The Ka = 1 transitions of H2S dimer and several isotopomers have been observed in a pulsed nozzle Fourier transform microwave spectrometer. These provide unambiguous evidence that H2S dimer has an anisotropic structure exhibiting S-H***S hydrogen bond. The hydrogen bond distance (H***S) is determined to be 2.778(9) Å, slightly smaller than the sum of van der Waals radii of H and S (∼3 Å). The hydrogen bond angle S-H***S is determined to be 175(7)°. The structure is similar to that of the well explored H2O dimer, though in bulk, ice and solid H2S appear very different. The structure determined from microwave spectroscopy is in very good agreement with the result from high level theoretical calculations.