Dipole moment and hyperfine properties of the ground state and the C–H excited vibrational state of HCN

Radio frequency transitions have been measured in the J=1 rotational level of HCN for both the ground vibrational state and the first excited state of the C–H stretching mode using molecular beam electric resonance spectroscopy. The vibrationally excited state was populated with an infrared laser. The dipole moment and hyperfine properties for the ground and excited states are 〈μ〉000=2.985 188(3)D, 〈μ〉001=3.017 408(4)D, 〈eQq〉000=−4707.83(6) kHz, 〈eQq〉001=−4661.39(8) kHz, 〈CN〉000=10.13(2) kHz, 〈CN〉001=10.06(3) kHz, 〈CH〉000=−4.35(5) kHz, 〈CH〉=−4.21(3) kHz.