The v2 = 1, 2 and v4 = 1 bending states of 15NH3 and their analysis at experimental accuracy

Abstract

15 NH 3 is the object of extensive investigation due to the central role of ammonia in astronomical sciences and to the complexity of modeling its interacting vibrationally excited states. Of major interest in astrochemistry is the determination of the 14 N/ 15 N ratio in space, characterized by unexpected variability among different solar system objects and reservoirs. Recently, the spectroscopic analysis of ground and v 2 = 1 a, s states of 15 NH 3 has been completed at experimental accuracy. Here, the characterization of the a, s inversion symmetry levels of v 2 = 1, 2 and v 4 = 1 states is presented. New spectra of 15 NH 3 have been recorded from 325 to 2000 cm −1 at a resolution ranging from 0.00096 cm −1 to 0.003 cm −1 , using the Canadian Light Source synchrotron at CLS. 7518 transitions covering nine bands, ν 2 , 2ν 2 , ν 4 , 2ν 2 ← ν 2 , ν 4 ← ν 2 , 2ν 2 ↔ ν 4 and the inversion-rotation transitions in the excited states, have been fitted simultaneously. The effective Hamiltonian adopted includes all symmetry allowed interactions between and within the studied excited states, according to the most recent results on ammonia. The transitions have been reproduced at experimental accuracy using 185 spectroscopic parameters, determined with high precision. The leading diagonal parameters, Gv, B, C, D's, compare well with those of 14 NH 3 . The wavenumbers of the assigned transitions are compared with their theoretically predicted values. An improved set of ground state parameters is also derived. These results noticeably improve the wavenumber line list in the high-resolution transmission molecular absorption (HITRAN) database.

Using HITRAN to Model Opacities for Planetary Atmospheres: Test case of Microwave Spectra of NH$_3$, SO$_2$ and PH$_3$

“…The inversion band for the 15 NH 3 molecule is also included in HITRAN based on the CDMS database (Müller et al, 2005;Endres et al, 2016) and (taking isotopic abundance into account) is approximately three orders of magnitude weaker than the principal isotopologue near 0.8 cm −1 . Additional, 15 NH 3 line position data comes from the work of Canè et al (2019) who investigate the ν 2 = 1, 2 and ν 4 = 1 bending states of 15 NH 3 . Also, some intensity data of 15 NH 3 comes from the work of Yurchenko (2015) who generated a theoretical room-temperature line list.…”

Laser absorption spectroscopy for plasma-assisted thermochemical treatment. Part I.: Applicability of the Beer–Lambert law and interpretation of spectroscopic data

“…The information about molecular properties, required for calculation of S(T), is available on-line in the HITRAN database [21]. For the molecular species relevant for this work, CH 4 , NH 3 , HCN, and CO, the data compiled from the works [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] are presented in [21]. The gas temperature to be considered has to be determined independently.…”

Optically Pumped Terahertz Molecular Laser: Gain Factor and Validation up to 5.5 THz

“…Additional information on this particular point can be found in Section 4.3. In the tables reported in this article, frequencies are those from the HITRAN database; [37][38][39][40][41] experimental values can differ and for some transitions, frequencies found in the JPL database [42] can be more accurate.…”