Triplet state harvesting and search for forbidden transition intensity in the nitrogen molecule

Abstract

Triplet excited states of the N2 molecule play an important role in electric discharges through air or liquid nitrogen accompanied by various afterglows. In the rarefied upper atmosphere, they produce aurora borealis and participate in other energy-transfer processes connected with atmospheric photochemistry and nightglow. In this work, we present spin–orbit coupling calculations of the intensity of various forbidden transitions, including the prediction of the electric dipole transition moment of the new 13Σg−← A3Σu+ band, which is strongly prohibited by the (+|−) selection rule, the new spin-induced magnetic B′3Σu−← A3Σu+ transition, magnetic and electric quadrupole transitions for the B3Πg← X1Σg+ Wilkinson band, and the Lyman–Birge–Hopfield a1Πg ← X1Σg transition. Also, two other far-UV singlet–singlet quadrupole transitions are calculated for the first time, namely, the Dressler–Lutz a"1Σg+–X1Σg+ and the less studied z1Δg–X1Σg+ weak transitions.

Nonadiabatic quantum dynamics explores non-monotonic photodissociation branching of N2 into the N(4S) + N(2D) and N(4S) + N(2P) product channels

“…This methodology was successfully applied to describe the electronic structure of N 2 and its cation multiple times. 49,50,56,57,68,77 An active space of 17 orbitals (4s u , 3s g , 4p u , 4p g , and 2d g ) for 10 valence electrons is employed in all computations. The two lowest 1s u and 1s g orbitals are not included in the active space but are fully optimized in the CASSCF procedure.…”

“…Quantum chemical calculations have accompanied experiments in interpretation of the electronic structure of N 2 in many directions: vibronic states energies and composition, 46,47 nature of electronic transitions 48,49 and band complexes. 50,51 The potential energy curves were studied in detail [52][53][54][55][56][57][58][59] as well as the spin-orbit 56 and nonadiabatic couplings. 60 Nowadays the quantum dynamical approaches [61][62][63][64] have reached a level where they can offer a computational tool which allowed us to follow the time-evolution of an electronic wave packet travelling in the forest of electronic states, beyond the states directly accessed from the ground electronic state.…”

Harnessing visible light: enhancing TiO2 photocatalysis with photosensitizers for sustainable and efficient environmental solutions

“…It is noteworthy that the excited electron, having a parallel spin relative to its unexcited, paired electron, transitions into the triplet state, which boasts a considerably longer lifetime. However, the return of the excited electron to the ground state in the triplet state is constrained by the Pauli exclusion principle, as this process is considered "spin forbidden" (Stoll and Schweiger, 2006;Li et al, 2022;Minaev et al, 2022). Consequently, the excited electron in the triplet state cannot simply revert to the ground level, leading to a substantially prolonged lifetime for the triplet state (Minaev et al, 2022).…”

“…However, the return of the excited electron to the ground state in the triplet state is constrained by the Pauli exclusion principle, as this process is considered "spin forbidden" (Stoll and Schweiger, 2006;Li et al, 2022;Minaev et al, 2022). Consequently, the excited electron in the triplet state cannot simply revert to the ground level, leading to a substantially prolonged lifetime for the triplet state (Minaev et al, 2022). These intricate dynamics play a pivotal role in determining the fate of the excited state and influence the subsequent photochemical and photophysical processes in which the photosensitizer is involved.…”