Infrared spectroscopy of NH+: An analysis of the perturbation between the X 2Π and a 4Σ− states

Abstract

Observation of the 43Σ+ g , 33Π g , 23Δ g , and b 3Π u states of 39K2 by perturbation facilitated optical-optical double resonance spectroscopy J. Chem. Phys. 102, 6646 (1995); 10.1063/1.469137 Laser spectroscopy of the A2Π-X2Σ+ transition of SrOH: Deperturbation analysis of Kresonance in the v 2=1 level of the A2Π state Determination of the internal state distribution of NO(X 2Π) produced in the O(3 P)+NH(X 3Σ−) reaction J. Chem. Phys. 97, 180 (1992); 10.1063/1.463606 Rotation-vibration analysis by finite difference perturbation technique. Application to 1Σ+ state of NHThe v = 1-0 vibration-rotation transitions in the X 2n and a 41; -states as well as those between the two electronic states were observed with a difference frequency laser as a radiation source. The two electronic states (X 2n and a 41; -) lie close together and interact each other strongly through the spin-orbit coupling. A merged least-squares fit was carried out with the present infrared transition wave numbers, some of the previous optical term values, and the recent far-infrared rotational transition frequencies to determine the spectroscopic parameters precisely. The equilibrium internuclear distance was obtained to be 1.0692 ± 0.0002 and 1.0924 ± 0.0001 A for the X and a states, respectively. The A-type doubling transition frequencies were calculated for several of the lowest J states with the molecular constants obtained and the hyperfine coupling constants determined from the far-infrared transitions.

The ISO LWS high-resolution spectral survey towards Sagittarius B2

“…The NH + ion is isoelectronic to CH and de Almeida & Singh (1982) have proposed that photoionization, charge transfer, radiative association and ion–molecule reactions in the gas phase may lead to a significant concentration of NH + in the ISM. Its ground state lines ( N = 1–1, J = 3/2–1/2) occur outside our survey range at 294.14 and 296.08 μm (Verhoeve et al 1986), but the second rotational transitions, N = 2–1, J = 5/2–3/2, do occur within the range at 160.01 and 159.70 μm (Kawaguchi & Amano 1988). However, these do not correspond to any of the unassigned lines.…”

Electronic structure of NH+: An ab initio study

“…A singular feature in Figure 1 is the near degeneracy between 3σ and 1π in the neighborhood of the minima of NH + and NH (1.0692 Å for the ion 11 and 1.0362 Å for the neutral 12). At the equilibrium distance of NH(X 3 Σ − ), for example, E = −0.5501 H and E = −0.5371 H, that is, 3σ and 1π are separated by only 0.013 H or 0.35 eV.…”

Microwave and submillimeter molecular transitions and their dependence on fundamental constants

“…However, there is an important difference: for NH + the first excited state 4 − lies only 340 cm −1 above the ground state [68,69]. The spin-orbit interaction between these states leads to strong perturbations of the rotational structure and of the -doublet splittings and to an additional enhancement of the sensitivity coefficients [58].…”