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A theoretical study of the dipole photoelectron angular distribution asymmetry parameter, β, of the 6s, 5s and 4s subshells has been conducted for a range of closed-shell heavy, Hg (Z = 80), Rn (Z = 86), Ra (Z = 88) and superheavy, No (Z = 102), Cn (Z = 112), Og (Z = 118), Ubn (Z = 120) elements to understand the deviation of β from the nonrelativistic value of 2 owing to relativistic effects. It was found that the deviation, strongest in Cooper minimum regions, persists over all energy for all ns subshells, and the deviations increase with Z. Three levels of relativistic calculations were performed in order to pinpoint the particular interactions responsible for the details of the behavior of the ns β’s as functions of energy, n, and Z and, in addition to the effects of the (relativistic) spin–orbit interaction, interchannel coupling was found to be of crucial importance in the determination of the β parameter in most of the situations studied.

High harmonic generation (HHG) is strongly modified near plasmonic nanostructures due to confinement and inhomogeneity of the electromagnetic field. Previous studies have revealed low-intensity generation of HHG and extension of the plateau; however, the roles of potential shape and a combination of inhomogeneous infrared (IR) and blue fields on HHG have not been studied. In this work, we study HHG driven by inhomogeneous two-color (800–400 nm) IR and blue femtosecond pulses by numerically solving the time-dependent Schrödinger equation. HHG spectra are computed for two different models: for a short-range potential, which supports a single-bound state, and for a long-range potential, which supports a Rydberg series, to show potential dependence on inhomogeneous two-color HHG. A substantial enhancement in the value of the cut-off resulting from inhomogeneity up to the ∼600th order, extending beyond the water window, is found for both the models. The HHG spectra are highly sensitive to the relative phase of the two-color fields and this sensitivity increases with increasing inhomogeneity. Possibilities of efficiently generating and controlling attosecond pulse train and isolated attosecond pulse are discussed.

The angular distribution and photoionization Wigner time delay of Xe 5s photoelectrons are studied in the region of the second Cooper minimum (SCM) using (i) the relativistic multiconfiguration Tamm–Dancoff approximation, (ii) the relativistic-random-phase approximation (RRPA) and (iii) the RRPA-with-relaxation to demonstrate how differing treatments of correlation, and the relativistic interactions, affect the results. The results of the three methods are compared with each other and with available experimental data. The comparison reveals the importance of electron correlations for which a multiconfiguration description of the initial state is essential. The spin-resolved and spin-averaged photoionization time delay results show important signatures in the region of the SCM in the Xe 5s photoionization cross-section.

Using methods related to the Lambert W function, we present solutions of two apparently different problems: (1) The one-dimensional double square well potential in quantum mechanics and (2) The transverse electric and magnetic modes for a step-index electromagnetic waveguide. The solution techniques provide insight into the bound energy states for the single and double square well problems and the allowed modes of propagation in a waveguide with varying refractive indices. The solutions can be viewed in either of two related complex plane representations. Comparison of the solution geometries suggests that interesting applications may be possible in nanostructures and devices which are designed to be sensitive to small changes in their environment.

Synopsis The effect of spin-orbit activated interchannel coupling (SOIAIC) has been studied on the time delay spectrum of 3d photoionization in xenon. The relativistic-random-phase-approximation with relaxation (RRPA-R) has been used to calculate the Wigner-Eisenbud-Smith (WES) time delay in photoionization. SOIAIC has a strong influence on the WES time delay for all ejection angles of the photoelectrons with respect to the incident direction and the polarization vector of the photon absorbed.

Synopsis Calculations of the photoionization cross sections for the superheavy atoms of atomic numbers 102, 112 and 118 have been performed using the relativistic-random-phase approximation (RRPA) which is based on the Dirac equation. The results show that relativistic effects cause anomalies in level ordering for some inner shells, and that interchannel coupling is of great importance.

Synopsis Avoided Crossings are one of the unique spectroscopic features of confined atomic system. Shannon’s information entropy as a predictor of these phenomena by varying the perturbation (confinement strength) on ground state and some of excited states of H atom is studied in this work. In addition to the energy level repulsion at avoided crossing, it is observed that Shannon’s entropy also assures the exchange of information of involved states, and also validates entopic uncertainty.

Synopsis Wigner time delay in photodetachment of Br− has been studied. The absence of Coulomb phase in photodetachment process makes the Wigner time delay more sensitive to the centrifugal barrier shape resonance and threshold effects. Important relativistic effects have been found near the threshold region.

Advances in optimizing thermoelectric material efficiency have seen parallel activities in theoretical and computational studies. In the current work, we calculate the exact Fermi–Dirac integrals to enable the generalization of the Wiedemann–Franz law (WF) in order to enhance the dimensionless thermoelectric figure of merit ZT = α 2 σ / κ . This is done by optimizing the Seebeck coefficient α, the electrical conductivity σ, and the thermal conductivity κ in terms of the Lambert W, and the generalized Lambert W functions (offset log). In the calculation of the thermal conductivity κ, we include both electronic and phononic contributions. The solutions provide insight into the relevant parameter space including the physical significance of complex solutions and their dependance on the scattering parameter r and the reduced chemical potential μ*.

An empirical ansatz for the complex photoionization amplitude and Wigner–Eisenbud–Smith time delay in the vicinity of a Fano autoionization resonance are proposed to evaluate and interpret the time delay in the resonant region. The utility of this expression is evaluated in comparison with accurate numerical calculations employing the ab initio relativistic random phase approximation and relativistic multichannel quantum defect theory. The indisputably good qualitative agreement (and semiquantitative agreement) between corresponding results of the proposed model and results produced by the ab initio theories proves the usability of the model. In addition, the phenomenology of the time delay in the vicinity of multichannel autoionizing resonances is detailed.

We investigate the case of resonance-induced deviations of the angular distribution anisotropy parameter, ?, from its nominal value of 2.0 for the Kr 4s-subshell at the 3d ? mp(m ? 5) excitations and the Xe 5s-subshell in the region of the 4d ? mp(m ? 6) excitations. We observe small but unmistakable variations of ? from 2.0 at these resonances. In the case of Kr the largest deviation from 2.0 is a mere -0.030(6), ? 4s ? 1.970(6), while in Xe it is definitively larger at -0.080(6), ? 5s ? 1.920(6). To understand these results in more detail, we have carried out relativistic random phase and relativistic multi-channel quantum defect calculations. Our theoretical results clearly indicate deviations of ? from 2.0 for these photolines in these resonance regions, although the degree of variation is predicted to be larger than what is observed. � 2006 IOP Publishing Ltd.

A study of the photoionization of spin–orbit split subshells of high-Z atoms confined in C60 has been performed using the relativistic-random-phase approximation. Specifically, Hg@C60 5p, Rn@C60 6p and Ra@C60 5d were investigated and the near-threshold confinement resonances in the j = l − 1/2 channels were found to engender structures in the j = l + 1/2 cross sections via correlation in the form of interchannel coupling. These structures are termed spin–orbit induced confinement resonances and they are found to profoundly influence the Wigner time delay spectrum resulting in time delays of tens or hundreds of attoseconds along with dramatic swings in time delay over small energy intervals. Pronounced relativistic effects in time delay are also found. These structures, including their manifestation in time delay spectra, are expected to be general phenomena in the photoionization of spin–orbit doublets in confined high-Z atoms.

Angular distributions of valence photoelectrons showing effects due to higher-multipole photon interactions have been measured for the first time. Neon 2s and 2p photoemission exhibits effects beyond the dipole approximation throughout the 250 - 1200 eV photon-energy range studied. The results suggest that any photoemission experiment, on any sample, can be affected at relatively low photon energies, pointing to a general need for caution in interpreting angle-resolved-photoemission measurements.

The results of calculations of the atomic photoionisation cross sections, angular distribution asymmetry parameters, branching ratios and spin polarisation parameters for the 4d, 4p, 4s, 3d and 3p subshells of palladium are reported. Calculations have been performed for a photon energy range of about 0.34-28.0 au. The positions of the Cooper minima in the 4d and 4p photoionisation cross sections are located in the continuum. Also, the study shows the 4s and 3p Cooper minima to be in the discrete part of the spectrum. The centrifugal barrier faced by the continuum f electrons causes a 'shape resonance' in the 4d and 3d cross sections and also affects the branching ratio for the sigma (nd5/2): sigma (nd3/2) cross sections. The branching ratio in the 4d cross section is influenced by the fact that the Cooper minima in the individual relativistic dipole, 4d5/2,3/2 to in f7/2,3/2 channels occur at different photon energies. Threshold effects and dynamical factors such as the occurrence of Cooper minima have a marked effect on the energy dependence of the spin polarisation parameters.

Photoionization cross-sections and photoelectron angular distributions for Ar 2p subshell in Ar, Ar6+ and Ar8+ are calculated using the relativistic MultiConfiguration Tamm-Dancoff Approximation (MCTD) [1] that takes into account certain non-RPA correlations.

The spin-orbit activated interchannel coupling is a purely relativistic effect that alters the partial photoionization cross sections of spin-orbit doublet channels. Presented is an exploration of how the spin-orbit activated interchannel coupling is affected by confinement in a C60 cage.

A state-of-the-art photoelectron spectroscopy (PES) experimental setup is designed and built to study the structure and dynamics of interstellar medium anions, in particular polyaromatic hydrocarbon chain (PAH) anions.

Wigner time delay has been studied in the shape resonance region for the outer nd→ef photoionization transitions in atomic Zn and Cd.

Wigner time delay for inner and outer shells of Ne@C60-5 have been studied using relativistic random phase approximation (RRPA) [1]. Coulomb confinement resonances (CCR) due to the charged nature of fullerene cause prominent effects on the photoionization time delay of 1s subshell. These CCRs in 1s also results in significant modifications of the time delay in 2s and 2p ionization channels through interchannel coupling at energies far above their thresholds.

Studies of the 2s → np autoionization resonances using a combination of Relativistic Random Phase Approximation (RRPA) and Relativistic Multichannel Quantum Defect Theory (RMQDT) of Mg isoelectronic sequence are reported.

Time delay in photoionization of a half-filled shell atom is predicted to be strongly term-dependent and subject to the dramatic impact of a giant autoionization resonance. Photoionization of the Mn atom is chosen as a case study.

Time delay in quadrupole (E2) channels is studied in atomic Hg using the Relativistic Random Phase Approximation. Interchannel coupling is found to be extremely important and large time delays are found in the region of quadrupole (E2) Cooper minima.

Quadrupole photoionization from valence and intermediate subshells of atomic mercury, radon and radium have been studied in the present work. Multiple Cooper minima in the E2 channels have been found even when only intra-shell inter-channel coupling is included, in contrast with the dipole case in which multiple Cooper minima were found only when inter-shell interchannel coupling was included.

A study of the outer 4s subshell of the Ca atom in a spherical attractive potential well (SAW) of variable depth is performed to determine the effect of an external potential on dipole (E1) and quadrupole (E2) photoionization processes. As the depth of the potential well increases, dramatic changes are observed in the 4s cross-section, as well as in the photoelectron angular distribution. The existence of Cooper minima in the 4s dipole channels give rise to very significant effects of quadrupole interactions, even at extremely low energies, in the vicinity of the E1 Cooper minimum. It is shown that the entrapment of Ca in a spherical attractive well (Ca@SAW) further enhances the importance of quadrupole interactions determining the photoionization parameters. The complicated behavior of both dipole and quadrupole Cooper minima, as functions of well depth, is delineated, along with the importance of relativistic effects.

Photoionization studies of outer shells of high-Z atoms like Radon (Z=86) and Radium (Z=88) have been studied using relativistic random phase approximation (RRPA) [1,2]. Multiple minima found in the pho-toionization cross section were attributed to many electron correlations resulting from interchannel coupling with photoionization channels from neighboring subshells. In the present work, we report the combined effect of confinement, correlation and relativistic interactions on the structure of these multiple minima in high-Z atoms by using the RRPA.

We report studies of photoelectron angular distribution and cross-section for photoionization of xenon 5s electrons using the relativistic multiconfiguration Tamm–Dancoff (MCTD) approximation. We find that MCTD provides a significantly improved agreement with experiment, compared to some of the other relativistic many body approximations such as the relativistic random phase approximation and the relativistic random phase approximation with relaxation, over the entire photon energy region bracketing the near-threshold 5s Cooper minimum, from the 5s threshold up to about 70 eV. The MCTD results in the length form are in much better agreement with the experiment than those in the velocity form, suggesting residual correlations that must be of importance.

The 3d core level photoemission of metallic Ag and In was measured over a wide energy range including the 2p ionization thresholds. The intensities (photoionization cross sections) of the 3d5/2 and 3d3/2 lines were observed to modulate significantly with photon energy, both absolute and relative, and this is most pronounced in the vicinity of the 2p thresholds, i.e., at photon energies about an order of magnitude above the 3d thresholds. Calculations based on the relativistic-random-phase approximation show that this effect is due to interchannel coupling of the 3d photoionization channels with the 2p channels affecting the cross section over a wide range of energies. It is argued that this is a general phenomenon in high-energy photoionization throughout the periodic table. � 2013 IOP Publishing Ltd.

The photoionization of Ba 5s in the high-energy Cooper minimum region has been investigated using the relativistic-random-phase approximation and the relativistic-random-phase approximation with relaxation. Comparison with recent experiment shows good agreement for the total cross section, but only qualitative agreement for the photoelectron angular distribution asymmetry parameter, β. The disagreement was traced to the omission of photoionization-plus-excitation channels arising from the 4d subshell.

Many electron correlation effects on dipole (E1) and quadrupole (E2) photoabsorption processes are investigated for the Ar isoelectronic sequence from Cl− to Cd30+.

Dipole and quadrupole photoionization parameters for intermediate subshells of mercury have been studied using the relativistic-random-phase-approximation (RRPA). Multiple Cooper minima are observed in 5d quadrupole cross sections, even at the level of intrashell coupling. It has been found that the effect of interchannel coupling is much more significant for dipole photoionization parameters than for quadrupole parameters.

The effect of interchannel coupling and confinement on the photoionization of the Kr atom is examined. It is found that the position of the Cooper minimum is sensitive to interchannel coupling in both free and confined Kr. The strengths of the confinement oscillations are also sensitive to interchannel coupling.

The combined effects of interchannel coupling, relativistic interactions and endohedral confinement on the photoionization of atomic Kr are studied. The confinement of the Kr atom placed at the centre of the C 60cage is modelled by placing the atom inside an annular spherical potential. Cross sections for the photoionization and angular distribution of photoelectrons from the 4p, 4s, 3d and 3p subshells are reported within the framework of the relativistic-random-phase approximation. � 2012 IOP Publishing Ltd.

Photoionization of Mg 3s is studied near the Cooper minimum in dipole channels using the relativistic-random-phase approximation. While the importance of first-order nondipole effects on photoelectron angular distributions at low energies is well known, it is reported here for the first time that in the energy region near the dipole Cooper minimum, quadrupole transitions are not just important, but actually dominate the total photoionization cross section. Studies of dipole-dipole, dipole-quadrupole and quadrupole-quadrupole interference terms in the photoelectron angular distribution show that in the region of dipole Cooper minimum even the calculation of the dipole angular distribution parameter, ?, requires the inclusion of quadrupole channels. The significance of second-order [O(k2r2)] nondipole terms, primarily due to the contributions from electric quadrupole-quadrupole interference terms at photon energy as low as ?11 eV, are shown to induce dramatic changes in the photoelectron angular distribution over a small energy range. � 2011 IOP Publishing Ltd.

The Multiconfiguration Tamm-Dancoff approximation (MCTD) is used to calculate the photoionization cross section of cadmium. Results are compared with available experimental data and also with earlier computations of the cross-section. We find that while earlier computations overestimated the photoionization cross section compared to experiment, the present MCTD computation underestimates the same.

The effect of a spin-orbit interaction activated interchannel coupling in 4d photoionization channels of Xe on the 5s photoionization amplitudes is studied and analysed. The dramatic effect of confinement of the Xe atom in a C60 cage on the 4d photoionization parameters and the consequent effect on 5s photoionization via an interchannel coupling are also discussed. � 2009 IOP Publishing Ltd.

Doppler-broadened absorption spectrum of rubidium (87Rb and 85Rb) D2 line has been studied in the presence of a magnetic field of intermediate strength i.e. up to 5mT. Resonant non - linear magneto optical rotation is measured in the Doppler broadened spectrum of rubidium atomic vapour. Low light intensity approximation in the intermediate field region has been made to calculate the magneto optical rotation and to compare with experimental data. The enhancement of non-linear magneto optical rotation is discussed taking into account hole burning and circular birefringence in the intermediate field region.

We report here 'allowed' and 'forbidden' electromagnetic transition amplitudes among various low lying states of doubly ionized Thallium (T12+) using relativistic coupled cluster method based on Dirac-Fock hybrid basis functions. These transitions are of importance in astrophysics and plasma research. The effect of core correlation, pair correlation and core polarization on these transitions are estimated.

These proceedings arose from the 7th Asian International Seminar on Atomic and Molecular Physics (AISAMP) which was held at the Indian Institute of Technology, Madras from 4–7 December 2006. The history of the AISAMP has been reviewed by Takayanagi http://www.physics.iitm.ac.in/~aisamp7/history.html. This international seminar/conference series grew out of the Japan–China meetings which were launched in 1985, the fourth of which was held in 1992 and carried a second title: The First Asian International Seminar on Atomic and Molecular Physics (AISAMP), thus providing a formal medium for scientists in this part of the world to report periodically and exchange their scientific thoughts. The founding nations of Japan and China were joined subsequently by Korea, Taiwan, India and Australia. The aims of the symposia included bringing together leading experts and students of atomic and molecular physics, the discussion of important problems, learning and sharing modern techniques and expanding the horizons of modern atomic and molecular physics. The fields of interest ranged from atomic and molecular structure and dynamics to photon, electron and positron scattering, to quantum information processing, the effects of symmetry and many body interactions, laser cooling, cold traps, electric and magnetic fields and to atomic and molecular physics with synchrotron radiation. Particular interest was evident in new techniques and the changes of the physical properties from atomic to condensed matter. Details of the 7th AISAMP, including the topics for the special sessions and the full programme, are available online at the conference website http://www.physics.iitm.ac.in/~aisamp7/. In total, 95 presentations were made at the 7th AISAMP, these included the Invited Talks and Contributed Poster Presentations, of which 52 appear in the present Proceedings after review by expert referees, refereed to the usual standard of the Institute of Physics journal: Journal of Physics B: Atomic, Molecular and Optical Physics. We received extensive support from the Journal of Physics: Conference Series staff; Graham Douglas, in particular, has been of tremendous help. The 7th AISAMP was very well attended and was sponsored primarily by the host Indian Institute of Technology, Madras (Chennai), the Board of Research in Nuclear Sciences, (Department of Atomic Energy, Government of India), the Department of Science and Technology, (Government of India), and the Asian Office of Aerospace Research and Development (AOARD) of the US Air Force. There was support from various quarters—each was invaluable and added to the success of the 7th AISAMP. We are very grateful to all the sponsors. It is superfluous to add that guidance and active participation from several colleagues within the host Institute was the primary source of strength for the actual organization of the conference and the multitude of arrangements for the organization came from the young graduate students at the IIT-Madras. We hope that this volume of Journal of Physics: Conference Series will be referenced widely and that it will strengthen ties between various countries in the region in and around Asia, and also of course to all scientists in this field the world over. Pranawa C Deshmukh, Purushottam Chakraborty and Jim F Williams Editors

A theoretical study of photoionization parameters of Hg atom confined in a spherical shell potential has been carried out using the relativistic random phase approximation. It is found that confinement, correlation and relativistic effects all bring significant and separate changes in the 6s photoionization cross-section, and also in the photoelectron angular distribution.

We have determined the amplitudes for Stark-induced (SI) transitions, of current interest in atomic physics and astrophysics, between mixed states dominated by same parity configurations of some low-lying states of singly ionized calcium. Well established Relativistic Coupled cluster (RCC) method has been used for the spectroscopic study of these transitions. This method has proved to be a very useful tool for rigorous electron correlation studies. We compare our results with experimental data for allowed electric dipole transition amplitudes and energies and also with other theoretical studies.

The triple differential cross section of Ca (4s2) in coplanar symmetric geometry at low impact energies is calculated using a spin averaged static exchange potential and a modified semi-classical exchange potential in Distorted Wave Born Approximation. The calculations have been carried out at incident energies of 10.11, 12.61, 19.61, 24.61, 34.61, 44.61, 54.61 and 64.61 eV for Ca, at which experimental data were available for comparison. The effect of post collision interaction has also been studied using Gamow factor introduced by Whelan et al. (1994). The present calculations have been compared with the recent (e, 2e) experimental studies of Murray (2005) and the earlier theoretical work of Chauhan et al. (2005). The present results are found to be in better agreement with experimental data as compared to the earlier study.

A systematic study of electric quadrupole (E2) photoionization electronic transitions from 4p, 4s and 3d subshells for atomic krypton is carried out in the photon energy range from their respective ionization thresholds up to photon energy of 1500 eV. Truncated relativistic random phase approximation (RRPA) is employed at different levels of interchannel coupling to study the effect of relativistic interactions and electron correlations. It is found that the E2 angular distribution asymmetry parameters are rather sensitive to interchannel coupling.

A study of the LIII X-ray absorption spectra of the rare earths Nd(Z=60), Sm(Z=62), Gd(Z=64), Dy(Z=66), and Yb(Z=70) in their sesquioxides is reported. The preabsorption observed in the spectra of Sm and Gd is attributed to the vacancies created in the 4f levels due to exposure of the sample of continuous X-rays. The near-edge structure of the spectra is interpreted on the basis of molecular orbital levels in these systems. The metal-oxygen average bond lengths are calculated using the Levy method and the results are found to be in good agreement with those obtained using a diffraction technique. The variation of bond lengths across the rare-earth series is discussed.

Simplifying assumptions made while considering complex systems often lead to non-orthogonal sets of wavefunctions. A procedure is suggested for employing such non-orthogonal wavefunctions without first orthogonalising them. The method involves the use of a basis reciprocal to the basis of the non-orthogonal functions. The relative intensities of K alpha 1, K beta 1 and K beta 2 X-ray spectral lines calculated by the proposed method are in fair agreement with available experimental data.

The cross section for K+ photoionisation has been calculated at the relativistic random-phase approximation level and found to be in excellent agreement with a recent experimental investigation.