The Ultraviolet Emission Spectra of OH⁺ and OD⁺. Rotational Structure and Perturbations in the A³Π_i–X³Σ⁻ Transition

Abstract

The A3Πi–X3Σ− emission systems of OH+ and OD+ have been reinvestigated in detail. Fourteen bands have been analyzed (of which seven are new), and accurate rotational constants have been obtained for the levels ν = 0–2 in the two states of OH+ and ν = 0–3 in the two states of OD+. Corrected assignments are given for the low J lines in the bands of OH+ (which are important in astrophysical spectra, such as those of H2O containing comets).The perturbations in the A3Π states of both isotopes have been studied quantitatively, and the erratic Λ doubling explained in detail. The position of the perturbing b1Σ+ state has been determined to within a few cm−1, and minor perturbations by the A1Δ state have been characterized. Values of the spin–orbit coupling constant, A, and the spin–spin interaction parameter, α, have been extracted from the data for OD+A3Π ν = 0.

High-resolution laser spectroscopy and photodissociation dynamics of OH+

“…An attempt was made to allow for a rotational dependence of H so R 10 , but no improvement in the fit was achieved. The T values for the A 3 Π state differ from those of [1] by a constant value of 4.41(16) cm -1 , the origin of which we have not been able to determine. In this section we describe dissociation from c 1 Π levels to form O + + H and O + H + , the partitioning between these dissociation channels and the mechanisms that govern the predissociation.…”

“…We have conducted a combined spectroscopic and dynamical study of photodissociation spectra (c 1 [1] to yield parameters for the four electronic states. The c 1 Π state is observed to predissociate from v = 1-6 and shows a remarkable selectivity in its dissociation to form O + + H and/or O + H + according to the e/f symmetry of the rotational level.…”

“…Spectroscopic studies of gas-phase OH + comprise a detailed analysis of the A 3 Π -X 3 Σ -electronic band system observed in emission (see [1] and references therein) and of longer wavelength transitions between levels of the X 3 Σ -ground state. The A 3 Π -X 3 Σ -electronic transition of 16 OH + exhibits perturbations between rotational levels of v = 1 of the A 3 Π state and v = 0 of the nearby b 1 Σ + state.…”

“…The A 3 Π -X 3 Σ -electronic transition of 16 OH + exhibits perturbations between rotational levels of v = 1 of the A 3 Π state and v = 0 of the nearby b 1 Σ + state. Merer et al [1] carried out a rotational analysis on the triplet system allowing for these perturbations and obtained molecular parameters for the electronic states as well as the first information on the location and some molecular parameters of the b 1 Σ + state. In the first spectroscopic fast-ion-beam experiment on OH + , Helm, Cosby and Huestis [2] studied a few transitions of the A 3 Π -X 3 Σ -system involving quasi-bound rotational levels of the A 3 Π state by Doppler-tuning the transitions into resonance with the lines of an argon ion laser.…”

Electron impact dissociation of H2O: emission cross sections for OH*, OH+*, H*, and H2O+* fragments

“…The OH + radical is isoelectronic to the NH-fragment which was investigated in a previous publication [26][27][28]. Merer et al [45] The (c 1H) excited state is unstable and predissociates quickly before it decays radiatively into the (a 1A) state [521.…”