Low-temperature spectroscopic measurements of the ‘dimol’ transitions of singlet molecular oxygen [O₂(a¹Δ_g)]

Active nitrogen and oxygen: Enhanced emissions and chemical reactions

“…Indeed, it is evident in the spectra at higher resolution in Fig. 3, in this work, that there are neither wide bands peaked at $633.4 and at $703.2 nm for the 0,0-0,0 and 0,0-0,1 2O 2 (a 1 D g ) emissions [28][29][30][31]39,40], nor the $761.8 nm band for the O 2 ðb 1 R þ g Þ emission [28][29][30][31][38][39][40]. There are also no singlet molecular oxygen peaks in the N 2 1pbs background afterglow emissions enhancement spectra of [18] in Fig.…”

“…The constants k 1 À k 5 were determined [26,27,30,[38][39][40][41]. In any event calculations show that even though there maybe a very large difference in concentration between N 2 (B 3 P g ) and O 2 ðb 1 R þ g Þ or 2O 2 (a 1 D g ), primarily the very large difference in lifetimes between them and secondarily the quenching (by O, N, NO, even O 3 , etc.)…”

“…However, O 2 (a 1 D g ) appears to be the most probable species to be responsible for the N 2 1pbs emissions intensity enhancements. This is due to the fact that all higher excited molecular oxygen species will be deactivated in the systems studied, before they can have a chance to contribute to the above N 2 1pbs background afterglow emissions intensity enhancements, since they have much lower radiative and collisional lifetimes [28][29][30][31][38][39][40] than the O 2 (a 1 D g ) species.…”

Dimol Emission of Oxygen Made Possible by Repulsive Interaction

“…The red light emitted by singlet molecular oxygen is a standard textbook example of chemiluminescence, , and has a long history of experimental − and theoretical ,− investigations. The energy of the strongest band of the emitted light is approximately twice as large as that of the vertical O 2 ( a 1 Δ g ) → O 2 ( X 3 ∑ g – ) transition, which is spin-forbidden.…”

“…Since the emission starts from short-lived excited species and requires the intermolecular interaction of two systems in which the corresponding transitions are forbidden individually, the signal is very weak and relatively hard to study experimentally. , The spectral characteristics, the band position and shape, along with their temperature dependence, were recorded long time ago, ,, while the corresponding rate constantswhich also require the determination of the concentration of the transient O 2 ( a 1 Δ g )were reported recently by Zagidullin et al , The theoretical investigations performed so far mostly concerned the potential energy surfaces of the electronic states − that determine the geometry and binding energy of the dimer complex. These studies showed that the O 2 –O 2 intermolecular potential is predominantly repulsive, and shows only a shallow van der Waals minimum at large intermolecular separation with very small binding energy …”