Laboratory Measurements of the Hyperfine Structure of H¹⁴N¹²C and D¹⁴N¹²C

The nuclear quadrupole hyperfine structure of H14N12C and D14N12C has been resolved in the laboratory for the first time using millimeter-wave absorption spectroscopy. The transient species were produced in a pulsed DC discharge nozzle, and Doppler broadening effects were minimized by propagating the millimeter waves coaxially with the supersonic molecular beam. New rest frequencies for the J = 1-0, J = 2-1, and J = 3-2 rotational transitions of the ground vibrational state were determined. The nuclear quadrupole coupling constants derived from the spectra are (eQq)N = 264.5 ± 4.6 kHz for H14N12C and (eQq)N = 294.7 ± 13.1 kHz and (eQq)D = 261.9 ± 14.5 kHz for D14N12C.