Dimol Emission of Oxygen Made Possible by Repulsive Interaction

Abstract

For the energy emitted in a textbook example of chemiluminescence, the peculiar red light produced by singlet molecular oxygen is about twice that of the spin-forbidden O(aΔ) → O(X∑) transition. Theoretical studies suggest that the O(aΔ)-O(aΔ) van der Waals interaction is weak, and at room temperature no long-lived complex is formed. Our high-level ab initio calculations show that in the bound domain of the dimer, the oscillator strength is very small, but increases at smaller intermolecular separations, where, however, the interaction is repulsive. We propose that the emission is induced by collisions: it takes place "on-the-fly", when the collision energy allows the system to access the repulsive part of the potential energy surface where the oscillator strength is relatively large. The contribution of different orientations of the two O molecules to the emission has been evaluated with a simple semiclassical model. The position of the emission peak is in accord with the experiment, and the estimated rate coefficient of collision-induced emission averaged over orientation is in reasonable agreement with the measurements.

An unrestricted approach for the accurate calculation of the interaction potentials of open-shell monomers: The case of O2–O2

“…7 Knowledge of the interaction potential is also of relevance in the study of the condensed phases of oxygen [8][9][10] where in recent years the study of the change in the nature of the intermolecular forces in solid oxygen as a function of pressure and the properties of the epsilon phase have been highly debated. [11][12][13] Even though significant efforts have been devoted to the detailed experimental and theoretical characterization of the (𝑂 2 ) 2 ground and excited states, 4,[14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] an accurate determination of its fundamental properties remains challenging. From molecular beam collision experiments 18 , a reasonable estimation of the isotropic radial coefficients for the dimer interaction has been obtained; however deriving from experimental measurements related anisotropic components that determine the angular dependence of the interaction or the splitting between the spin multiplets is much more difficult 25 (this issue will be further discussed in the Results and Discussion section).…”

A New Two-molecule Combination Band as a Diagnostic of Carbon Monoxide Diluted in Nitrogen Ice on Triton

“…We term such a band a twomolecule combination band, which is also known in the literature as a "dimol absorption band," dimol meaning "two-molecule." For example, see Ida et al (2010) and Tajti et al (2017). Previous identifications of twomolecule combination bands in spectra of ice samples include single photons exciting the fundamental mode of adjacent N 2 molecules (Grundy et al 1993) and adjacent N 2 and O 2 molecules (Minenko & Jodl 2006) as well as single photons exciting an electronic tran-…”

Polyatomic radiative association by quasiclassical trajectory calculations: Cross section for the formation of HCN molecules in H + CN collisions

“…There are only a few quantum dynamics studies where radiative association of triatomic molecules has been considered in full dimension including the following molecules [32][33][34][35][36][37][38][39] : HeH + 2 , H − 3 , HN − 2 , AlH + 2 , AlD + 2 , NaH + 2 , NaD + 2 , HCO − , HCO. For other polyatomic cases, either reduced dimensional semiclassical dynamical calculations 40,41 or statistical rate theories [42][43][44][45] are applied to obtain their rate constant.…”