Low-temperature high-resolution absorption spectrum of14NH3in theν1+ν3band region (1.51 μm)

Jet-cooled spectra of (NH3)-N-14 and (NH3)-N-15 in natural abundance were recorded using cavity ring-down (CRDS, 6584-6670 cm(-1)) and cavity enhanced absorption (CEAS, 6530-6700 cm(-1)) spectroscopy. Line broadening effects in the CRDS spectrum allowed lines with J ''-values between 0 and 3 to be identified. Intensity ratios in (NH3)-N-14 between the jet-cooled CRDS and literature room-temperature data from Sung et al. (J. Quant. Spectrosc. Radiat. Transfer, 113 (2012), 1066) further assisted the line assignments. Ground state combination differences were extensively used to support the assignments, providing reliable values for J, K and inversion symmetry of the ground state vibrational levels. CEAS data helped in this respect for the lowest J lines, some of which are saturated in the CRDS spectrum. Further information on a/s doublets arose from the observed spectral structures. Thirty-two transitions of (NH3)-N-14 were assigned in this way and a limited but significant number (19) of changes in the assignments results, compared to Sung et al. or to Cacciani et al. (J. Quant. Spectrosc. Radiat. Transfer, 113 (2012), 1084). Sixteen known and 25 new low-J transitions were identified for (NH3)-N-15 in the CRDS spectrum but the much scarcer literature information did not allow for any more refined assignment. The present line position measurements improve on literature values published for (NH3)-N-15 and on some line positions for (NH3)-N-14.