Determination of the dipole moment of H3N–SO3 in the gas phase

The dipole moment of the partially bonded molecule H3N–SO3 has been measured by microwave spectroscopy in the gas phase. The value obtained, 6.204(11) D, is over 4 times the sum of the individual monomer moments. The results are discussed in the context of recent speculations as to the complexʹs role in the nucleation of atmospheric aerosols.