A 1 Π → X 1 Σ + fluorescence in the NO + molecular ion observed after Auger decay of the 1 s −1 π* resonances of the N*O molecule and NO* was studied theoretically. The energies and probabilities of the transition between the vibrational levels of the electronic states, determining the excitation and Auger decay of the resonances of the nitrogen monoxide molecule and further radiation-induced decay of the NO + molecular ion were calculated by the first principles method. Multiplet splitting of the resonances of N*O and NO* and interference of the amplitudes of excitation of the molecule through various vibrational levels of the intermediate resonance explain the observed dependences of the intensity of A 1 Π(υ′) → X 1 Σ + (υ″) fluorescence on the excitation radiation energy. The discrepancies between the calculated and experimental integrated intensities of fluorescence point to the necessity of studying cascade processes determined by radiation transitions in NO + , including dipole transitions with a changed net spin.

The photoionization and photodissociation of an oxygen molecule are investigated theoretically by the method of coupled differential equations. The molecular orbitals of the core are calculated in the MO LCAO approximation. The molecular orbitals of a photoelectron in the discrete and continuous spectra are determined by the single-center method. The wave functions of vibrational motion of the oxygen molecule are obtained within the diabatic approach. The described method is used for calculating the predissociation and autoionization widths of the 2σ u −1 (c 4Σ u − )n/σg, v Rydberg states of the oxygen molecule. The total cross sections of the resonant photoionization and neutral predissociation calculated for the oxygen molecule in the excitation energy range 20.6–24.8 eV are in good agreement with the available experimental data.

The dynamics of predissociation of the 2σ u −1 (c 4Σ u − ), v vibrational states of the O 2 + ion was studied theoretically using the method of coupled differential equations. The main equations describing the vibrational motions of nuclei in the adiabatic and diabatic approximations are given. The applicability scope of approximate methods for solving these equations was studied. The predissociation widths for the v = 0 and 1 vibrational levels were found to be Γ0 = 0.054 meV and Γ1 = 9.71 meV. This substantiated the results of recent observations of neutral fragments formed after the dissociation of the O2 molecule. About 99% of the O 2 + ions in the 2σ u −1 (c 4Σ u − ), v states were found to decompose to the O(1 D) + O+(4 S) dissociation products.

Dispersed fluorescence from fragments formed after the de-excitation of the1s-1π* resonances of N*O and NO* has beenmeasured in the spectral range of 118–142 nm. This range is dominated bylines of atomic nitrogen and oxygen fragments and by the \(A ~^{1}{\rm \Pi}\left(v^{\prime}\right) \rightarrow X ~^{1}{\rm \Sigma}^{+}\left(v^{\prime \prime}\right)\) bands in the NO+ ion which result from the participator Auger decay of the 1s-1π* resonances. Ab-initio calculations of the transition probabilities between vibrationallevels during the reaction NO \(X~^{2}{\rm \Pi}\left(v_{0}=0\right)\rightarrow \) N*O\(\left( {\rm NO}^{\ast}\right) \) \(1s^{-1}\pi^{\ast }\left( v_{r}\right) \) ⇒ NO\(^{+}~A~^{1}{\rm \Pi}\left(v^{\prime}\right) \rightarrow X~^{1}{\rm \Sigma}^{+}\left(v^{\prime \prime}\right)\) were used to explain the observed intensity dependence for the \(A\left(v^{\prime }\right) \rightarrow X\left(v^{\prime \prime}\right)\) fluorescence bands on the exciting-photon energy acrossthe resonances and on both v′ and v′′vibrational quantum numbers. The multiplet structure of the 1s-1π* resonance and lifetime vibrational interference explain the observed exciting-photon energy dependence of the \(A\left( v^{\prime}\right) \rightarrow X\left(v^{\prime \prime}\right)\) fluorescenceintensity. A strong spin-orbit coupling between singlet and triplet statesof NO+ is proposed to reduce additional cascade population of the \(A~^{1}{\rm \Pi}\) state via radiative transitions from the\(W~^{1}{\rm \Delta}\) and \(A^{\prime}~^{1}{\rm \Sigma}^{-}\) states and to explainremaining differences between measured and calculated integral fluorescenceintensities.