C. Lavín

Quantum defect orbital study of the sodium isoelectronic sequence

The quantum defect orbital (QDO) method and its relativistic (RQDO) counterpart have been applied to the calculation of oscillator strengths for the 3s 2S → 3p 2Po, 3p 2Po → 3d 2D, 3d 2D → 4f 2Fo, and 3d 2D → 5f 2Fo transitions in sodium-like atoms. The consequences of including relativistic effects are demonstrated.

RYDBERG ELECTRON TRANSITIONS IN THE METHYL RADICAL

Abstract Transition probabilities corresponding to one-photon transitions to Rydberg states of the methyl radical have been calculated with a molecular-adapted version of the quantum defect orbital (QDO) method. The results appear to be in accord with those of an analysis of the experimental spectrum by Herzberg.

SYSTEMATIC IN THE RELATIVISTIC OSCILLATOR STRENGTHS FOR FINE-STRUCTURE TRANSITIONS IN THE ALUMINIUM ISOELECTRONIC SEQUENCE

Abstract Theoretical oscillator strengths for 3s 2 3p 2 P-3s 2 3d 2 D, 3s 2 3p 2 P-3s 2 4s 2 S and 3s 2 4s 2 S-3s 2 4p 2 P fine-structure transitions in some ions of the aluminium isoelectronic sequence are reported. The computations have been carried out with two formalisms within the context of quantum defect theory: the quantum defect orbital method (QDO) and its relativistic counterpart (RQDO). The advantages of including relativistic effects are made apparent. Some of these are reflected by the correct systematic trends displayed by the RQDO −values along the isoelectronic sequence.

Quantum-defect studies of transitions in the diffuse spectral series of the potassium isoelectronic sequence

Abstract Theoretical oscillator strengths are reported for transitions in the diffuse spectral series of some members of the potassium isoelectronic sequence (KI-CrVI). The calculations have been performed with the Quantum Defect Orbital (QDO) method. A core-polarization correction to the dipole transition moment has also been included in the formalism.

THE SPECTRUM OF NEH : A COMPARATIVE ISOELECTRONIC STUDY

Abstract Einstein coefficients and oscillator strengths for Rydberg–ground and Rydberg–Rydberg transitions in the rare-gas excimer NeH have been calculated with the quantum defect orbital (QDO) method. A comparative study of analogous transitions in NeH and in some of its isoelectronic Rydberg radicals has revealed clear similarities between them.

Multi-configuration Dirac-Fock and relativistic quantum defect orbital study of triplet-triplet transitions in beryllium-like ions

Abstract Oscillator strengths for 2s2p3P-2s3d3D and 2s2p3P-2s3s3S fine structure transitions in beryllium-like ions (Z = 4–36) have been calculated using both the Relativistic Quantum Defect Orbital (RQDO) method, with and without explicit inclusion of core-valence correlation, and the multiconfiguration Dirac-Fock (MCDF) approach. Our f-values, which are of interest in astrophysics and fusion plasma research, are compared with other theoretical and experimental results for the cases for which these are available.

Partial photoionization cross sections of NH4 and H3O Rydberg radicals.

Photoionization cross sections for various Rydberg series that correspond to ionization channels of ammonium and oxonium Rydberg radicals from the outermost, occupied orbitals of their respective ground states are reported. These properties are known to be relevant in photoelectron dynamics studies. For the present calculations, the molecular-adapted quantum defect orbital method has been employed. A Cooper minimum has been found in the 3sa(1)-kpt(2) Rydberg channel of NH(4) beyond the ionization threshold, which provides the main contribution to the photoionization of this radical. However, no net minimum is found in the partial cross section of H(3)O despite the presence of minima in the 3sa(1)-kpe and 3sa(1)-kpa(1) Rydberg channels. The complete oscillator strength distributions spanning the discrete and continuous regions of both radicals exhibit the expected continuity across the ionization threshold.

Ground and excited states of NH4: Electron propagator and quantum defect analysis

Vertical excitation energies of the Rydberg radical NH4 are inferred from ab initio electron propagator calculations on the electron affinities of NH4+. The adiabatic ionization energy of NH4 is evaluated with coupled-cluster calculations. These predictions provide optimal parameters for the molecular-adapted quantum defect orbital method, which is used to determine Einstein emission coefficients and radiative lifetimes. Comparisons with spectroscopic data and previous calculations are discussed.

Relativistic oscillator strengths for transitions in the principal spectral series of the silver isoelectronic sequence

In a very recent paper [1] we have reported oscillator strengths for fine structure transitions between levels belonging to the diffuse and sharp spectral series in the silver isoelectronic sequence. The calculations were performed with the quantum defect orbital method in both their non-relativistic (QDO) and relativistic (RQDO) formulations, with both implicit and explicit allowance for core-valence polarisation. We now present a parallel study of transitions belonging to thens2S−n′2P(n=5, 6;n′=5−10) spectral series of the AgI sequence, up toZ=63 in some cases.

Angular distribution of photoelectrons in small molecules: a molecular quantum defect calculation.

The molecular quantum defect orbital (MQDO) method, previously used in the determination of molecular photoionization cross sections, is applied here to calculate the angular distribution of photoelectrons arising from the molecular photoionization. Calculations are performed for the ionization from outer valence orbitals of HF, H(2)O, NH(3), N(2)O, and H(2)CO molecules. The results are compared with previous measurements and with theoretical curves found in the literature. Profiles of the angular distribution parameter as a function of photoelectron energy covering a range from the photoionization threshold to 120 eV are presented for the above molecules. The energy dependence of the angular distributions predicted by the MQDO calculations agrees fairly well with predictions from more sophisticated theories and with observed results.