Theoretical electric dipole moments of SiH, GeH and SnH

Accurate theoretical dipole moments have been computed for the X2Pi ground states of Si(-)H(+) (0.118 D), Ge(+)H(-) (0.085 D), and Sn(+)H(-) (0.357 D). The trend down the periodic table is regular and follows that expected from the electronegativities of the group IV atoms. The dipole moment of 1.24 + or - 0.1 D for GeH recently derived by Brown, Evenson and Sears (1985) from the relative intensities of electric and magnetic dipole transitions in the 10-micron spectrum of the X2Pi state is seriously questioned.