Effective Quantum Number Research Articles

STRUCTURE AND OSCILLATOR STRENGTH DENSITIES NEAR LⅡ,Ⅲ EDGES OF ARGON

The high resolution fast electron energy loss spectrum for inner shell 2p electron excitation and ionization of argon has been measured in present work at an electron impact energy of 2500eV and a mean scattering angle of 0°. The ionization limits and effective quantum numbers have been- deduced.- The oscillator strength densities for discrete transitions and two ionization continua were- also- determined.

Fine-structure effects on collisional broadening and shift of thallium two-photon lines.

Broadening and shift rates by rare gases have been measured for the Tl transitions 6${\mathit{P}}_{1/2}$-${\mathit{nP}}_{1/2,3/2}$ (n=9-14) applying Doppler-free two-photon spectroscopy. The rates show a clearly significant dependence on the total angular momentum of the upper nP states and also a distinct behavior over the most interesting range of intermediate effective principle quantum numbers. Calculations using a van der Waals potential and a combination of polarization and Fermi pseudopotential describe these dependences well. \textcopyright{} 1996 The American Physical Society.

On the binding of electrons to nitromethane: Dipole and valence bound anions

Conventional (valence) and dipole-bound anions of the nitromethane molecule are studied using negative ion photoelectron spectroscopy, Rydberg charge exchange and field detachment techniques. Reaction rates for charge exchange between Cs(ns,nd) and Xe(nf ) Rydberg atoms with CH3NO2 exhibit a pronounced maximum at an effective quantum number of n*≊13±1 which is characteristic of the formation of dipole-bound anions [μ(CH3NO2)=3.46 D]. However, the breadth (Δn≊5, FWHM) of the n-dependence of the reaction rate is also interpreted to be indicative of direct attachment into a valence anion state via a ‘‘doorway’’ dipole anion state. Studies of the electric field detachment of CH3NO−2 formed through the Xe(nf ) reactions at various n values provide further evidence for the formation of both a dipole-bound anion as well as a contribution from the valence bound anion. Analysis of the field ionization data yields a dipole electron affinity of 12±3 meV. Photodetachment of CH3NO−2 and CD3NO−2 formed via a supersonic expansion nozzle ion source produces a photoelectron spectrum with a long vibrational progression indicative of a conventional (valence bound) anion with a substantial difference in the equilibrium structure of the anion and its corresponding neutral. Assignment of the origin (v′=0, v″=0) transitions in the photoelectron spectra of CH3NO−2 and CD3NO−2 yields adiabatic electron affinities of 0.26±0.08 and 0.24±0.08 eV, respectively.

An experimental study of the deviation from equilibrium in a high-pressure microwave helium plasma produced by an axial injection torch

The distribution of atomic states for a helium plasma torch at high (atmospheric) pressure has been determined by calculating the populations of some excited states of the neutral helium system by means of different spectroscopic techniques. A plasma not close to local thermodynamic equilibrium was found. The overpopulation of some states showed that it was an ionizing plasma with the equilibrium deviation parameter of the ground state, , of about 100. The population of the excited states closely obeyed the law, where p is the effective principal quantum number.

FT Pulsed ESR/Electron Spin Transient Nutation Spectroscopy in the Study of Molecular Based Magnetism: Applications to High-Spin Polymers and Ferromagnetic Materials

Abstract Recently, organic high-spin polymers and clusters have been emerging. With the increasing effective molecular spin quantum number S and molecular weight of the polymers, however, cw ESR spectroscopy manifests its inherent disadvantages in discriminating high spins from S=½ and in determining the S's for the complex mixture of various spin assemblages. An electron spin transient nutation method based on pulsed ESR spectroscopy has been for the first time applied to a quasi 1D high-spin polymer as one of the most complex amorphous spin assemblages, identifying that the polymer is comprised of high-spin assemblages with the S's greater than two. It can be concluded that electron spin transient nutation spectroscopy is a facile and useful method for the exclusive identification of S and ESR transitions even for the cases of apparently vanishing fine-structure splittings and for spin systems with residual fine-structure terms in the spin Hamiltonian. Fundamental bases for the transient nutation method...

Summary of the IRON and OPACITY Projects

Considerable effort has been made recently by international collaborations, exploiting advances in atomic physics and in supercomputing, to compute complete sets of accurate data for astrophysically important processes; in particular, the Opacity Project and the IRON Project.The Opacity Project computed atomic data for opacity calculations• for H, He, Li, Be, B, C, N, O, F, Ne, Na, Mg, Al, Si, S, Ar, Ca, Fe.• energies of terms having effective quantum numbers v≤10 and total angular momentum L≤3 or 4, all spin and parity combinations;• gƒ-values for all dipole transitions between these bound terms;• total cross sections for photoionizaion from all calculated bound terms, tabulated on a grid of photon energies suitable to describe the resonance structure in sufficient detail to calculate reliable opacities;• line broadening parameters.28 key research papers arising from the Project, together with calculated energies and oscillator strengths for light ions, are reprinted in ‘The Opacity Project Volume 1’ (Opacity Project Team, 1994, IOP Publ. ISBN 0 7503 0288 7). All data are available from TOPbase, an on-line database at the CDS (Cunto et al. 1993, A&A 275, L5).The IRON Project aims to systematically compute electron excitation cross sections for the iron group of elements. Particular attention is given to requirements for the interpretation of data from specific space observations.In the first stage of the Project excitation cross sections have been computed for fine-structure transitions in the ground configuration of all ions of astrophysical interest. These data are essential for the interpretation of IR lines to be observed by ISO, as well as for coronal spectra.

Photoionization of the Be isoelectronic sequence from the ground and the 1S bound excited states.

Theoretical photoionization spectra below the 2p threshold of the Be isoelectronic sequence from the ground and a few selected $^{1}$S bound excited states are calculated using a B-spline-based configuration-interaction approach. The resonant structures of the doubly excited autoionization series following photoionization from different initial states are analyzed in detail in terms of various initial- and final-state multielectron interactions. In addition, our calculation has shown that the resonant widths vary smoothly as functions of the effective principal quantum number \ensuremath{\nu} along the autoionization series and approach approximately an expected ${\ensuremath{\nu}}^{\mathrm{\ensuremath{-}}3}$ dependence as \ensuremath{\nu} increases.

Evolution of barium autoionizing Stark spectra with energy and field.

Extensive calculations and measurements of barium autoionizing Stark spectra below the 5d ionization thresholds are presented. The theoretical description is based on a combination of R-matrix calculations in zero external field and a Harmin-Fano-type field-dependent frame transformation. In addition to verifying the basic validity of this approximation scheme, we examine the scaling of calculated resonance linewidths with energy. Under certain circumstances, the average linewidths are found to scale approximately as ${\ensuremath{\nu}}^{\mathrm{\ensuremath{-}}4}$, with \ensuremath{\nu} the relevant effective quantum number. Extreme departures from this scaling are observed for individual resonances, however, which could be important for the theoretical description of other processes in an electric field, such as dielectronic recombination.

Polarizabilities of cesium S, P, D, and F states

The scalar and tensor polarizabilities of over sixty S, P, D, and F states of cesium are evaluated using a Coulomb approximation. The expected scaling of polarizabilities as n ∗7, where n ∗ is the effective principal quantum number, was found to hold well for the higher excited states. The computed results agree closely with experimental measurements which are reviewed.

Doubly excited3Se,3De and3Ge states of two-electron atomic systems

Time-dependent perturbation theory has been applied to calculate the doubly excited triplet statesNsns:3Se,Npnp:3De andNdnd:3Ge (N=2, 3, 4,n=N+1, ... ,5) for He, Li+, Be2+ and B3+. A time-dependent harmonic perturbation causes simulataneous excitation of both the electrons with a change of spin state. The doubly excited energy levels have been identified as the poles of an appropriately constructed linearized variational functional with respect to the driving frequency. In addition to the transition energies, effective quantum numbers of these doubly excited states have been calculated and analytic representations of their wave functions are obtained. These are utilized to estimate the Coulomb repulsion term for these states which checks the consistency of the wave functions. These wave functions may also be used for calculating other physical properties of the systems.

Radiative Lifetimes of Some 5d10n2F and 5d10n2P Levels of Hg+

Abstract Radiative lifetimes of 8p2P3/1 (15.3 ns) and nf2F (7f2F5/2 - 24.7 m. 7f2F7/2 - 5.5 ns, 8f2F7/2 - 48.5 ns, 8f2F5/2 - 47.0 ns) levels of Hg+ have been measured employing delayed coincidence method. The dependencies of radiative lifetimes vs effective principal quantum number for np2P3/2 and np2F7/2 series are non linear.

High-resolution field ionizer for state-selective detection of Rydberg atoms in fast-beam laser spectroscopy

The design of a novel electrode structure for electric-field ionization of Rydberg atoms in a fast atomic beam is described. It allows the resolution of the ion signal from Rydberg atoms with adjacent effective principal quantum numbers n* in the range of 14≤n*≤40 and minimizes the volume where field ionization takes place. These features drastically reduce the number of background events arising from collisions of fast atoms with residual gas molecules and thus are essential for trace analysis applications of the technique of resonance ionization spectroscopy in collinear geometry.

Photoionization of ground and excited states of neon type Ti XIII

The R-matrix method is used to calculate the photoionization cross-section of Ti XIII from its ground and first three excited states. The results are obtained for photon energies ranging from the first ionization threshold to just above the second ionization threshold of the residual ion Ti XIV. Configuration interaction wavefunctions are used to describe the initial Ti XII and final Ti XIV states. The positions and effective quantum numbers for the Rydberg series converging to the excited state 2s2p6 2Se of the residual ion, are predicted.

Ladderlike ionization of the mercury atom in Hg-Ar low-pressure discharge and its modeling

A collisional-radiative model for hydrogen plasma has been reviewed in order to evaluate the ionization process through the high-lying levels of the mercury atom. Experimentally observed population densities of the mercury atom near its series limit have shown an x*−6 dependence (x* is the effective principle quantum number) as is predicted from the collisional-radiative model for an ionizing plasma. This fact suggests that a ladderlike ionization process accounts for a missing ionization process found in a previous model calculation for the mercury-argon low-pressure discharge [J. Appl. Phys. 68, 5052 (1990)]. An effective rate coefficient for the ladderlike excitation and ionization has been determined and introduced into the model equation. Electric and optical characteristics as well as the population densities of the excited atoms in the positive column have been calculated and compared with the experimental result. Significant improvement in agreement is obtained. The ladderlike excitation and ionization via high-lying levels of the mercury atom have been shown to occupy 10%–20% of the total ionization rate in the discharge considered.

Atomic data for opacity calculations. XXI. The neon sequence

Photoabsorption processes are studied for the ground and excited terms of the members of the neon isoelectronic sequence considered to be of significant astrophysical abundance. A two-state, LS close-coupling calculation is carried out. Oscillator strengths and total photoionization cross section data are calculated for even and odd LS terms with S=0,1;L<or=4, and an effective principal quantum number nu <or=10.

Influence of the lower state perturbation on the broadening and shift of optical lines of neon involving quasi-Rydberg states

The Omont-Kaulakys-Ueda treatment of collisional effects on optical lines involving Rydberg states in the intermediate region of the effective quantum number n* is modified. A simple method of calculating the broadening and shift cross-sections, including the perturbation of the lower state, is proposed and applied to the Ne-He and Ne-Ne systems.

Observation and analysis of core-penetrating Rydberg states of calcium monofluoride.

Optical-optical double-resonance fluorescence excitation spectra of molecular Rydberg states of CaF are reported, and states up to 45 500 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ above the X $^{2}\mathrm{\ensuremath{\Sigma}}^{+}$ ground state are rotationally analyzed. The new electronic states are arranged into six ``core-penetrating'' Rydberg series by fitting their energies to the Rydberg equation using effective principal quantum numbers. The ionization potential of CaF is thereby determined to be 46 998\ifmmode\pm\else\textpm\fi{}5 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. Spin-orbit, \ensuremath{\Lambda}-doubling, and spin-rotation constants are determined for a subset of the observed states. Scaling relationships for each of these fine-structure effects are developed and shown to yield characteristic scaling parameters for each series. Analysis, using ${\mathrm{Ca}}^{+}$ atomic orbitals as a basis set for the molecular Rydberg orbitals, shows that each of the six observed molecular Rydberg series correlates with a core-penetrating Rydberg series of the ${\mathrm{Ca}}^{+}$ ion, and that the p\ensuremath{\sim}d mixing suggested by the spin-orbit scaling parameters of the $^{2}\mathrm{\ensuremath{\Pi}}$ states is consistent with that previously determined for low-lying states using a ligand-field model. The spin-orbit scaling parameter for the lone $^{2}\mathrm{\ensuremath{\Delta}}$ series is consistent with pure l=2 character. In the lowest-lying state of each series, n\ensuremath{\sim}(n+1) mixing is shown to account for deviations of the molecular constants from scaling predictions based on the corresponding constants of the higher-lying states. The coefficients of scaling relations for the \ensuremath{\Lambda}-doubling and spin-rotation constants reveal interseries interactions which are consistent with substantial l mixing and which suggest that multistate perturbation and/or multichannel quantum-defect analyses should be pursued.

Microwave forced autoionization of Na2 Rydberg states.

We have examined the ionization of ${\mathrm{Na}}_{2}$ Rydberg states of principal quantum number n=11--16 converging to rotational-vibrational, v=3--6 and R10, states of ${\mathrm{Na}}_{2}^{+}$ by 8-GHz microwave fields. Rydberg states lying below the lowest, v=0, R=0 (v and R are the vibrational and rotational quantum numbers of the molecular ion), ion limit of ${\mathrm{Na}}_{2}^{+}$ are observed to ionize at approximately E=1/3${\mathit{n}}_{0}^{5}$, where ${\mathit{n}}_{0}$ is the effective quantum number relative to the v=R=0 limit. The agreement with this dependence is not nearly as good as in an atom, and the possible reasons for the deviations are discussed.

Relativistic electric dipole radial integrals between Rydberg atomic states in the semiclassical Coulomb approximation

Analytic wave functions are obtained from the Klein-Gordon equation by using the quantum-defect theory in the semiclassical Coulomb approximation. From this result, analytic expressions for relativistic electric dipole radial integrals between highly excited Rydberg states χλ, χ'λ' are calculated in terms of Anger functions plus an algebraic part combination of sin (πs) and cos(πs), where s=(σ'/gs)(χ'− χ)−(σ/σ')(χ− χ), χ= χχ' · χ , λ, σ and χ', λ', σ' are the relativistic effective principal quantum numbers, orbital angular momenta and charges of states involved. In the nonrelativistic limit, we retrieve classical formulas established previously in the dipole case.

Hyperfine-interaction constants of the 8D3/2 state in 85Rb using quantum-beat spectroscopy.

Quantum beats due to the hyperfine interaction were observed in the radiative decay of the 8${\mathit{D}}_{3/2}$ state in $^{85}\mathrm{Rb}$. The data agree well with theory allowing determination of the magnetic-dipole (\ensuremath{\Vert}a\ensuremath{\Vert}=0.879\ifmmode\pm\else\textpm\fi{}0.008 MHz) and electric-quadrupole (\ensuremath{\Vert}b\ensuremath{\Vert}=0.15\ifmmode\pm\else\textpm\fi{}0.02 MHz) (a/b&gt;0) hyperfine constants. The results are consistent with those obtained for other ${\mathit{D}}_{3/2}$ states in $^{85}\mathrm{Rb}$ and $^{87}\mathrm{Rb}$. The observed magnetic-dipole constants for the ${\mathit{nD}}_{3/2}$ n&gt;7 states of $^{85}\mathrm{Rb}$ are given to within 2% by the relation a(MHz)=252/${\mathit{n}}^{\mathrm{*}3}$ where ${\mathit{n}}^{\mathrm{*}}$ is the effective principal quantum number.