Magda Fifirig

Dissociative excitation in electron collisions with HD

In the framework of the multi-channel quantum defect theory (MQDT), we have performed nonrotational computations for the dissociative excitation cross section of HD+ initially in the vibrational level vi+ (vi+=0, vi+=1 or vi+=2) of the electronic ground state, with electrons of energy ranging from 2 to 12 eV. Considering the case of energy-independent interactions, the reaction matrix K is evaluated in the second order of the Born expansion of the Lippmann–Schwinger equation.

Electron-induced processes in H+2, D+2 and T+2

We investigate the isotopic effects on the cross sections of the dissociative excitation, dissociative recombination, vibrational excitation and vibrational de-excitation of the homonuclear hydrogen molecular cations with electrons of energy above the dissociation threshold of the electronic ground state. The computations were accomplished using an improved numerical code based on a previous work (Fifirig and Stroe 2008 Phys. Scr. 78 065302).

Phase dependence of three-colour two-photon ionization of hydrogen

We consider a ground-state hydrogen atom interacting with a three-colour electromagnetic field, taken as the superposition of a fundamental frequency ω and two consecutive odd harmonics of order 2p-1 and 2p + 1 (p≥2 and integer), with constant relative phase differences. We study in the lowest-order perturbation theory the process of ionization due to the net absorption of energy 2pω. The ionization rate is controlled by the relative phase difference δ between the harmonics, which modifies the interference terms. We present an analysis of both the angular electron distribution and the total rate, which shows that the interference effects are influenced by the order of the harmonics and their intensity ratio.

Dissociation of vibrationally excited by electrons

We have investigated the electron impact dissociation of the deuterium molecular cation assuming a Franck–Condon distribution of the initial vibrational states given by electron impact ionisation of D2. The electron energy range 1–12 eV has been considered. The relative contributions of the initial vibrational states to the total cross-sections of the dissociative recombination and excitation have been determined.

Two-colour three-photon ionization of hydrogen

Based on analytical equations valid in perturbation theory, we study the process of ionization of the ground state of the hydrogen atom by the absorption of three photons, two of them being of the same frequency. Results are given for the total ionization rate and for the angular distribution of the ejected electrons, in a regime of frequencies in which two-colour two-photon ionization is not possible. The case of orthogonal photon polarizations, investigated in some detail, displays a strong dependence on the electron direction.

Dissociation of 14N2+ ions induced by slow electrons

The cross sections and thermal rate coefficients for the dissociative recombination (DR) of the molecular nitrogen ions initially in the first four vibrational levels of the ground electronic state have been computed in the framework of the multichannel quantum defect theory. An energy range of 0.001–1 eV has been considered. The contribution of the indirect DR mechanism involving Rydberg states associated with the first excited ion core has also been investigated.

Competition between reaction channels in electron collisions of vibrationally excited

The competing processes taking place in the reactive collisions of vibrationally hot with electrons, namely dissociative recombination, dissociative excitation, vibrational excitation, elastic scattering and vibrational de-excitation have been studied using a theoretical approach based on the multichannel quantum defect theory. The energy range considered is 0.1–12 eV. The high sensitivity of these processes to the initial vibrational state of is illustrated. In the case of a Franck–Condon distribution of initial vibrational levels, the comparison with the recent experimental results is performed.

Dissociative excitation of HD +, D 2+, and DT + by electron impact

In the framework of the Multi-Channel Quantum Defect Theory (MQDT), a theoretical study of the dissociative excitation is presented. Numerical results for the dissociative excitation cross sections of HD+, D2+, and DT+ with electrons of energy between 2 and 12 eV are reported. The contribution of the vibrational continua of the two lowest electronic states as explicit ionization channels has been considered. Within a quasi-diabatic representation of the molecular electronic states, the Born expansion of second order is done in the K-matrix evaluation.

Electron impact on vibrationally cold

The dissociative recombination and vibrational excitation processes induced by electron impact on vibrationally cold are investigated in the framework of the multichannel quantum defect theory for electron energies below 1 eV. The thermal rate coefficients for the electron temperature range from 10 to 5000 K are reported.

Electron-induced vibrational transitions in N2+

We have investigated the vibrational excitation and de-excitation of with electrons of energy below 1 eV. Computations have been performed using the multichannel quantum defect theory with a second-order perturbative evaluation of the K reaction matrix. Assuming a Maxwellian electron-energy distribution, the corresponding rate coefficients were also determined.