The microwave spectrum of isoselenocyanic acid,HNCSe

A new molecular species has been detected by passing HBr gas through dry AgNCSe, which is shown by consideration of the rotational constants of the four isotopic species H¹⁴N¹²C⁸⁰Se, H¹⁴N¹²C⁷⁸Se, H¹⁴N¹³C⁸⁰Se and D¹⁴N¹²C⁸⁰Se to be HNCSe. The spectrum is consistent with that of a quasilinear molecule. A preliminary structure has been determined having r(HN) = 0.99 A, r(NC) = 1.95 A, r(CSe) = 1.717 A and a mean HNC angle of 143°. The quadrupole interaction parameter eQq = 1.17 MHz and the dipole moment component μ_a = 1.98 D have also been determined.