Final-state Wave Function Research Articles

Photoionization of water molecules by high energy photons

We theoretically study the photoionization of water molecules by high energy photon impact. We develop a model in which the final state wavefunction is given by a Coulomb continuum wavefunction with effective charges and the water molecule bound states are represented using the Moccia's monocentric wavefunctions. We obtain analytical expressions for the transition matrix element that enable the computation of cross sections by numerical quadratures. We compare our predictions for photon energies between 20 and 300 eV with more elaborated theoretical results and experiments. We obtain a very good agreement with experiments, in particular, at enough high energies where there is a lack of elaborated results due to their high computational cost.
 Received: 15 March 2017, Accepted: 25 June 2017; Edited by: S. Kais; DOI: http://dx.doi.org/10.4279/PIP.090006
 Cite as: L Martini, D I R Boll, O A Fojón, Papers in Physics 9, 090006 (2017)
 This paper, by L Martini, D I R Boll, O A Fojón, is licensed under the Creative Commons Attribution License 3.0.

Precise test of internal-conversion theory: αK measurements for transitions in nine nuclei spanning 45 ≤ Z ≤ 78

We have been testing the theory used to calculate internal-conversion coefficients (ICCs) by making a series of measurements of αK values with precision better than ±2%. So far we have measured E3 transitions in three nuclei, 103Rh, 111Cd and 134Cs; and M4 transitions in six nuclei, 119Sn, 125Te, 127Te, 137Ba, 193Ir and 197Pt. Together, these span a wide range of A and Z values. In all cases, the results strongly favor Dirac-Fock calculations in which the final-state electron wave function has been computed in an atomic field that includes the vacancy created by the internal-conversion process.

Single electron transfer in He+-He+ collision and production of helium atom

The four body Born distorted wave (BDW-4B) approximation with correct boundary condition is used for single electron transfer in He+-He+ collision. The post and prior total cross sections are obtained in the energy range 10–1000 keV/amu and the post-prior discrepancy is estimated. The sensitivity of the results with respect to the choice of the final helium-like ground state wave function is evaluated through two different wave functions. The importance of the dynamic electron correlations is tested as a function of impact energy. Additional experimental data at higher impact energies is needed for a better assessment of the validity of the present theory.

The Triple Differential Cross Sections for Electron Impact Ionization of Metastable 3s State Hydrogen Atoms with Exchange Effect

A final state wave function of multiple scattering theory developed by Das and seal is utilized in the present study to calculate the triple differential cross sections (TDCS) for the ionization of metastable 3S state hydrogen atoms at incident electron energy of 250 eV with the exchange effects in the asymmetric coplanar geometry for various kinematic conditions. Our present calculation results are compared with the available hydrogenic ground state experimental data and other existing theoretical results. A good qualitative agreement is shown with those of compared results of the present study specifically with hydrogenic ground state experimental data and metastable 2S and 2P state with exchange effect results. These new results offer an extensive scope for experimental verification in such ionization process.

Calculations of Photocurrent from BP and its band structures

We present here the results of photocurrent from boron pnictides namely BP. The photocurrent in this system had been calculated by using three types of potential namely free- electron, Kronig-Penney and Muffin-Tin potentials. Schrodingers’ equation has been solved by using these potentials to obtain the necessary initial and final state wave-functions for the electrons. These wave-functions are used for evaluating the matrix element ⟨ Ψf\\p.A + Ap\\Ψi⟩ which is involved in the formula of photocurrent.

Low-energy photodetachment ofGa−and elastic electron scattering from neutral Ga

We present a comprehensive study of the photodetachment of the negative gallium ion and elastic electron scattering from neutral Ga for photon and electron energies ranging from threshold to 12 eV. The calculations are carried out with the $B$-spline $R$-matrix method. A multiconfiguration Hartree-Fock method with nonorthogonal term-dependent orbitals is employed to generate accurate initial- and final-state wave functions. The close-coupling expansions include the $4s{\phantom{\rule{0.16em}{0ex}}}^{2}4pnl(kl)$ bound and continuum states of Ga and the $4s$-excited autoionizing states $4s4{p}^{2}$. The calculated photodetachment and elastic cross sections exhibit prominent resonance features. In order to clarify the origin of these resonances, the contributions of the major ionization channels to the partial cross sections are analyzed in detail.

NUMEN Project @ LNS : Heavy Ions Double Charge Exchange as a tool towards the 0νββ Nuclear Matrix Element

The NUMEN Project, proposed at INFN Laboratori Nazionali del Sud (LNS) in Catania, has the aim to access the nuclear matrix elements, entering the expression of the life time of double beta decay, by relevant cross sections of double charge exchange reactions. The basic point, on which it is based this innovative technique, is the coincidence of the initial and final state wave-functions in the two classes of processes and the similarity of the transition operators. A key aspect of the Project is the use of MAGNEX large acceptance magnetic spectrometer, for the detection of the ejectiles, and of the INFN LNS K800 Superconducting Cyclotron (CS), for the acceleration of the required high resolution and low emittance heavy-ion beams.

FDMX: extended X-ray absorption fine structure calculations using the finite difference method.

A new theoretical approach and computational package, FDMX, for general calculations of X-ray absorption fine structure (XAFS) over an extended energy range within a full-potential model is presented. The final-state photoelectron wavefunction is calculated over an energy-dependent spatial mesh, allowing for a complete representation of all scattering paths. The electronic potentials and corresponding wavefunctions are subject to constraints based on physicality and self-consistency, allowing for accurate absorption cross sections in the near-edge region, while higher-energy results are enabled by the implementation of effective Debye-Waller damping and new implementations of second-order lifetime broadening. These include inelastic photoelectron scattering and, for the first time, plasmon excitation coupling. This is the first full-potential package available that can calculate accurate XAFS spectra across a complete energy range within a single framework and without fitted parameters. Example spectra are provided for elemental Sn, rutile TiO2 and the FeO6 octahedron.

Calculations of Triple Differential Cross-Sections for the Ionization of H (3S) by Electron Impact

In the present study we have calculated the Triple Differential Cross-Sections (TDCS) for the ionization of metastable 3S-state hydrogen atoms at 250 eV incidence electron energy for various kinematic conditions in the asymmetric coplanar geometry. A final state wave function of multiple scattering theory [11] has been used in the present study. The present results show a good qualitative agreement with the existing hydrogenic ground state experimental data and various related theoretical results. Some results of hydrogenic metastable states are also presented here for comparisons. However there is no existing theoretical and experimental works on hydrogenic metastable 3S-state except an existing theoretical first born result of Vuc<img width="7" height="16" src="http://article.sciencepublishinggroup.com/journal/122/1221089/image001.png" />i<img width="7" height="16" src="http://article.sciencepublishinggroup.com/journal/122/1221089/image001.png" /> et al. [19].

Electron-impact dissociation cross sections of vibrationally excited He molecular ion

Electron-impact cross sections for the dissociation process of vibrationally excited He molecular ion, as a function of the incident electron energy are calculated for the dissociative transition by using the R-matrix method in the adiabatic-nuclei approximation. The potential energy curves for the involved electronic states and transition dipole moment, also calculated with the R-matrix method, were found to be in good agreement with the results reported in literature. The vibrationally resolved dissociation cross sections of He exhibit a resonant structure around 7 eV. The observed strong variation of the magnitude of this structure with the vibrational level is explained in terms of the overlap of initial and final (continuum) state wave functions in the Franck–Condon region.

Heavy-ion double charge exchange reactions: A tool toward $0 \nu\beta\beta$ nuclear matrix elements

The knowledge of the nuclear matrix elements for the neutrinoless double beta decay is fundamental for neutrino physics. In this paper, an innovative technique to extract information on the nuclear matrix elements by measuring the cross section of a double charge exchange nuclear reaction is proposed. The basic point is that the initial and final state wave functions in the two processes are the same and the transition operators are similar. The double charge exchange cross sections can be factorized in a nuclear structure term containing the matrix elements and a nuclear reaction factor. First pioneering experimental results for the 40Ca(18O,18Ne)40Ar reaction at 270 MeV incident energy show that such cross section factorization reasonably holds for the crucial 0+ --> 0+ transition to 40Args, at least at very forward angles.

Heavy Ions Double Charge Exchange reactions: towards the 0νββ Nuclear Matrix Element determination

First experimental results, obtained at the INFN-LNS laboratory in Catania, for the 40Ca(18O,18Ne)40Ar reaction at 270 MeV are shown. The data give encouraging indication on the capability to access quantitative information towards the determination of the Nuclear Matrix Elements for 0νββ decay. The idea is to use an innovative technique to access the nuclear matrix elements entering the expression of the life time of the double beta decay by cross sections measurements of double charge exchange reactions. The basic point is the coincidence of the initial and final state wave-functions in the two classes of processes and the similarity of the transition operators, which in both cases present a superposition of Fermi-like, Gamow-Teller-like and rank-two tensor components with a relevant implicit momentum available in the intermediate channel.

The role of nuclear reactions in the problem of 0νββ decay and the NUMEN project at INFN-LNS

An innovative technique to access the nuclear matrix elements entering the expression of the life time of the double beta decay by relevant cross sections of double charge exchange reactions is proposed. The basic point is the coincidence of the initial and final state wave-functions in the two classes of processes and the similarity of the transition operators, which in both cases present a superposition of Fermi, Gamow-Teller and rank-two tensor components with a relevant implicit momentum transfer. First pioneering experimental results obtained at the INFN-LNS laboratory for the 40Ca(18O,18Ne)40Ar reaction at 270 MeV, give encouraging indication on the capability of the proposed technique to access relevant quantitative information. A key aspect of the project is the use of the K800 Superconducting Cyclotron (CS) for the acceleration of the required high resolution and low emittance heavy- ion beams and of the MAGNEX large acceptance magnetic spectrometer for the detection of the ejectiles. The use of the high-order trajectory reconstruction technique, implemented in MAGNEX, allows to reach the high mass, angular and energy resolution required even at very low cross section. The LNS set-up is today an ideal one for this research even in a worldwide perspective. However a main limitation on the beam current delivered by the accelerator and the maximum rate accepted by the MAGNEX focal plane detector must be sensibly overcome in order to systematically provide accurate numbers to the neutrino physics community in all the studied cases. The upgrade of the LNS facilities in this view is part of this project.

Photoionization ofFe7+from the ground and metastable states

The $B$-spline Breit-Pauli $R$-matrix method is used to investigate the photoionization of ${\mathrm{Fe}}^{7+}$ from the ground and metastable states in the energy region from ionization thresholds to 172 eV. The present calculations were designed to resolve the large discrepancies between recent measurements and available theoretical results. The multiconfiguration Hartree-Fock method in connection with $B$-spline expansions is employed for an accurate representation of the initial- and final-state wave functions. The close-coupling expansion includes 99 fine-structure levels of the residual ${\mathrm{Fe}}^{8+}$ ion in the energy region up to $3{s}^{2}3{p}^{5}4s$ states. It includes levels of the $3{s}^{2}3{p}^{6},3{s}^{2}3{p}^{5}3d,3{s}^{2}3{p}^{5}4s$, and $3s3{p}^{6}3d$ configurations and some levels of the $3{s}^{2}3{p}^{4}3{d}^{2}$ configuration which lie in the energy region under investigation. The present photoionization cross sections in the length and velocity formulations exhibit excellent agreement. The present photoionization cross sections agree well with the Breit-Pauli $R$-matrix calculation by Sossah et al. and the TOPbase data in the magnitude of the background nonresonant cross sections but show somewhat richer resonance structures, which qualitatively agree with the measurements. The calculated cross sections, however, are several times lower than the measured cross sections, depending upon the photon energy. The cross sections for photoionization of metastable states were found to have approximately the same magnitude as the cross sections for photoionization of the ground state, thereby the presence of metastable states in the ion beam may not be the reason for the enhancement of the measured cross sections.

Electron Impact Ionization of Metastable 3S-State Hydrogen Atoms by Electrons in Coplanar Geometry

In this work we have calculated first born triple differential cross sections (TDCS) for ionization of metastable 3S- state hydrogen atoms by electrons. In this study the final state wave function is described by a multiple scattering theory for ionization of hydrogen atoms by electrons. Results show qualitative agreement with other existing theoretical results for ionization of hydrogen atoms from metastable 2S-state and 2P-state. There are no other available results for ionization of hydrogen atoms from metastable 3S-state. The present result offers an extensive scope for experimental verifications in such ionization process.

Mapping spin-orbit activated interchannel coupling

Recent advances in the generation of femtosecond extreme ultraviolet pulses have opened up the possibility to study final-state wave functions in photoemission experiments. Here, we investigate, for the first time using femtosecond time-resolved core-level spectroscopy, the feasibility of observing the buildup of a state correlation in a direct time domain. Giant changes in the ratio of photoemission cross-sections of spin-orbit split core states, the branching ratio, are identified. Multi-configuration Dirac-Fock calculations show that the origin of the branching ratio deviation is due to strong core-valence interactions. The possibility to tune this interaction by charge transfer offers intriguing opportunities to study correlation effects in solid and molecular systems in the future.

Investigation of the unbound21C nucleus via transfer reaction

The cross section of the transfer reaction 20 C(d,p) 21 C at 30.0 MeV is investi- gated. The continuum-discretized coupled-channels method (CDCC) is used in order to obtain the final state wave function. The smoothing procedure of the transition matrix and the channel-coupling effect on the cross section are discussed.

Precise test of internal-conversion theory: Transitions measured in five nuclei spanning 50≤Z≤78

In a research program aimed at testing calculated internal-conversion coefficients (ICCs), we have made precise measurements of αK values for transitions in five nuclei, 197Pt, 193Ir, 137Ba, 134Cs and 119Sn, which span a wide range of A and Z values. In all cases, the results strongly favor calculations in which the final-state electron wave function has been computed using a potential that includes the atomic vacancy created by the internal-conversion process.

Atomic photoionization in a changing plasma environment

We present a detailed theoretical study on the photoionization of one- and two-electron atoms subject to an external changing plasma environment based on the Debye-H\"uckel model. Specifically, by examining the migration of the bound excited states into the continuum in the presence of plasma, our investigation has led to resonancelike photoionization structures immediately above the ionization thresholds for H, H${}^{\ensuremath{-}}$, and He atoms. For He, unlike the usual Fano-Beutler resonances due to the configuration mixing between the doubly excited components and the single ionization channel with different ${\ensuremath{\ell}}_{1}{\ensuremath{\ell}}_{2}$ angular momenta combinations in the final-state wave function, these plasma-induced resonancelike structures result from the mixing of the quasibound and continuum components of the same ${\ensuremath{\ell}}_{1}{\ensuremath{\ell}}_{2}$ combination in the final-state function. With a number of specific examples, we show that the general features of these spectra could be linked directly to the overlap at small $r$ between the effective wave functions of the outgoing ionized electron and the atomic electron in its initial states.

The double ionization of H2 by fast electron impact: Influence of the final state electron-electron correlation

We have determined fully differential cross sections of the (e, 3e) double ionization of H2 by employing correlated initial- and final-state wave functions. We have constructed for the description of the two slow ejected electrons a symmetrized product of a correlation function and two-center continuum wave functions, which fulfill the correct boundary conditions asymptotically up to the order O((kr)−2). We have shown that the introduction of the correlated part of the final-state wave function improves the results on the (e, 3-1e) of H2.