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University of Windsor

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Full-Text Articles in Physics

Influence Of Fringing Fields On The Field-Induced Quantum Beats Of Atomic Hydrogen, Gordon W. F. Drake Jan 1977

Influence Of Fringing Fields On The Field-Induced Quantum Beats Of Atomic Hydrogen, Gordon W. F. Drake

Physics Publications

Calculations are presented which include exactly the effects of fringing fields on the electric-field-induced quantum beats of atomic hydrogen. The results explain some recently observed phaseshifts of the quantum beats relative to the predictions of the 'sudden approximation'. The general features produced by finite rise-time and overshoot are discussed.

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Vector-Coupling Approach To Orbital And Spin-Dependent Tableau Matrix Elements In The Theory Of Complex Spectra, Gordon W. F. Drake, M. Schlesinger Jan 1977

Vector-Coupling Approach To Orbital And Spin-Dependent Tableau Matrix Elements In The Theory Of Complex Spectra, Gordon W. F. Drake, M. Schlesinger

Physics Publications

The power of the Young tableau scheme for labeling a complete spin-adapted basis set in the theory of complex spectra lies in one's ability to evaluate matrix elements of irreducible tensor operators directly in terms of the tableau labels and shapes. We show that the matrix-element rules stated by Harter for one-body operators can be easily derived from simple vector-coupling considerations. The graphical method of angular momentum analysis is used to derive closed-form expressions for the matrix elements of two-body operators. This study yields several interesting new relationships between spin-dependent operators and purely orbital operators. © 1977 The American Physical …

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Spin-Orbit Parameters By The Gelfand-Harter Method-A Test Calculation, J. Drake, Gordon W. F. Drake, M. Schlesinger Jan 1977

Spin-Orbit Parameters By The Gelfand-Harter Method-A Test Calculation, J. Drake, Gordon W. F. Drake, M. Schlesinger

Physics Publications

The spin-orbit parameters for the sextet states of the f5 configuration are computed using the Young-tableau techniques developed by Harter. The conceptual and computational advantages over traditional methods are discussed. © 1977 The American Physical Society.

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Quantum Beats In The Electric-Field Quenching Of Metastable Hydrogen, A. Van Wijngaarden, E Goh, Gordon W. F. Drake, P. S. Farago Jan 1976

Quantum Beats In The Electric-Field Quenching Of Metastable Hydrogen, A. Van Wijngaarden, E Goh, Gordon W. F. Drake, P. S. Farago

Physics Publications

The strong field-induced quantum beats observed in beam-foil studies of Ly- alpha radiation are obtained in a conventional metastable-hydrogen quenching experiment. The phase relation between the Stark shifted 2s 1/2- 2p 1/2 Lamb-shift oscillations and the much more rapid 2s 1-2p 3/2 fine-structure oscillations depends on the detailed way in which the quenching field is switched on. Apart from a phaseshift, the results agree with a non-perturbative theoretical calculation which assumes that the field is applied suddenly. Various frequency components of the time-dependent radiation intensity are identified with specific hyperfine transitions or groups of transitions. No adjustable parameters are used …

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Relativistic Corrections To Spin-Forbidden Electric-Dipole Transitions, Gordon W. F. Drake Jan 1976

Relativistic Corrections To Spin-Forbidden Electric-Dipole Transitions, Gordon W. F. Drake

Physics Publications

Theoretical results for spin-forbidden electric-dipole transitions have recently been questioned on the grounds that relativistic corrections to the transition operator were not included. It is shown here that these corrections are automatically included when the transition operator is expressed in the dipole length form. The above criticism of previous dipole-length calculations is therefore unfounded. The 1s2p 3P1-1s21S0 and 1s2p 3P1-1s2s 1S0 transitions of helium are discussed as specific numerical examples.

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Calculated Anisotropies For The Quenching Radiation In The Hydrogen Isoelectronic Sequence, Gordon W. F. Drake, C. P. Lin Jan 1976

Calculated Anisotropies For The Quenching Radiation In The Hydrogen Isoelectronic Sequence, Gordon W. F. Drake, C. P. Lin

Physics Publications

Accurate values of the Lamb shift can be derived from measurements of the anisotropy in the angular distribution of the radiation accompanying the electric field induced 2s-1s transition of hydrogen. Calculations of the anisotropy, including relativistic and hyperfine structure corrections, are presented for the hydrogenic ions up to S15+. The data enable the calculation of the Lamb shift from a measured value of the anisotropy. © 1976 The American Physical Society.

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Comments On A New Mathematical Technique In The Theory Of Complex Spectra, J Drake, Gordon W. F. Drake, M. Schlesinger Jan 1975

Comments On A New Mathematical Technique In The Theory Of Complex Spectra, J Drake, Gordon W. F. Drake, M. Schlesinger

Physics Publications

A large body of work on the algebraic properties of the Gelfand labelling scheme for atoms with several electrons has recently been synthesized by Harter (see abstr. A31652 of 1974) into a compact procedure for the construction of total angular momentum eigenfunctions and the evaluation of angular coefficients. Certain ambiguities in the procedure are removed. Also, an improved method for the diagonalization of the angular momentum matrix in the Galfand basis set is presented. As an example, the doublet states of the f 3 configuration are discussed.

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Improved Quantum Calculation Of The Vibrational Excitation Of H2 In Collinear Collisions With Helium, Gordon W. F. Drake, A. R. Holtg Jan 1975

Improved Quantum Calculation Of The Vibrational Excitation Of H2 In Collinear Collisions With Helium, Gordon W. F. Drake, A. R. Holtg

Physics Publications

The vibrational excitation probabilities of H2 in collinear collisions with He are calculated quantum mechanically, using the Fredholm integral method. Important differences are found when the accurate H2 molecular potential of Kolos and Wolniewicz (1968) is used instead of the less accurate Morse potential used extensively in previous work. The approximation of truncating the infinite set of coupled equations describing the collision problems is tested, and an alternative closure approximation is suggested to provide an indication of the effect of truncation on the results.

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Interaction Of Multilevel Atoms With Classical Time-Dependent Fields, Gordon W. F. Drake, R. B. Grimley Jan 1975

Interaction Of Multilevel Atoms With Classical Time-Dependent Fields, Gordon W. F. Drake, R. B. Grimley

Physics Publications

A wide class of problems is considered involving the interaction of multilevel atoms with classical time-dependent fields switched on at a definite time. It is shown that the exact time-dependent Green's function can be written as the particular solution to an inhomogeneous differential equation involving derivatives with respect to the external field variables. Asymptotic expansions are discussed and analytic solutions found for several cases. The time and frequency distributions of radiation emitted by a field-perturbed atom are calculated by including the radiation field as a first-order perturbation. © 1975 The American Physical Society.

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Erratum: Semiclassical Study Of The Vibrational Excitation Of H2 In Collision With He (J. Phys. B: Atom. Molec. Phys. (1974) 7 (398405)), Gordon W. F. Drake, C. S. Lin Jan 1974

Erratum: Semiclassical Study Of The Vibrational Excitation Of H2 In Collision With He (J. Phys. B: Atom. Molec. Phys. (1974) 7 (398405)), Gordon W. F. Drake, C. S. Lin

Physics Publications

No abstract provided.

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Semiclassical Study Of The Vibrational Excitation Of H2 In Collision With He, Gordon W. F. Drake, C. S. Lin Jan 1974

Semiclassical Study Of The Vibrational Excitation Of H2 In Collision With He, Gordon W. F. Drake, C. S. Lin

Physics Publications

The vibrational excitation and dissociation probabilities of H2 in a collinear collision with He are calculated, using the semi-classical time-dependent method along with the accurate H2 molecular potential of Kolos and Wolniewicz (1965, 1968). The complete set of bound and continuum eigenfunctions are represented in terms of a truncated basis set of harmonic oscillator functions. The results differ significantly from the Morse potential quantum mechanical calculations of Clark and Dickinson (1973). In addition, a state-dependent interaction potential is suggested to allow for the different average sizes of the H2 molecule in its initial and final states. The state dependent potential …

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Leading Radiative Correction To The Magnetic Dipole Transition Probability, Gordon W. F. Drake Jan 1974

Leading Radiative Correction To The Magnetic Dipole Transition Probability, Gordon W. F. Drake

Physics Publications

It has recently been suggested that a radiative correction of relative order ln may contribute to the 1s2sS13-1s2S01 magnetic dipole transition of the heliumlike ions. The low-frequency contributions to the correction are evaluated and shown to vanish. © 1974 The American Physical Society.

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Energies And Z-Expansion Coefficients For The D States In The Helium Sequence, P. Blanchard, Gordon W. F. Drake Jan 1973

Energies And Z-Expansion Coefficients For The D States In The Helium Sequence, P. Blanchard, Gordon W. F. Drake

Physics Publications

Non-relativistic variational energies for the 1s3d(1,3D) states of the helium isoelectronic sequence are calculated with a 50-term correlated basis set for Z=2-10, where Z is the nuclear charge, and the corresponding Z-expansion coefficients found through sixth order by fitting the energies to a series in Z-1. A variational-perturbation calculation of these coefficients through eleventh order (with the same basis set) is presented for comparison, and agreement is satisfactory. The 3d energies obtained by summing the Z-expansion perturbation series are found to yield excellent approximations to the variational values. The calculations are extended to the 1s4d( 1,3D) states to furnish variational …

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Photon-Scattering Theory Of The Quenching Of Hydrogenic Metastables, Gordon W. F. Drake, R. B. Grimley Jan 1973

Photon-Scattering Theory Of The Quenching Of Hydrogenic Metastables, Gordon W. F. Drake, R. B. Grimley

Physics Publications

The quenching of hydrogenic metastables is formulated as a near-resonant photon-scattering problem, and a complete analysis of the polarization and angular distribution of the emitted radiation is presented. The contribution from np states with n>2 is calculated, and an alternative method of measuring the Lamb shift is suggested. © 1973 The American Physical Society.

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Eigenvalues Of The 2p3pp3 And 2p3dd1,3 Bound States Of The Helium Isoelectronic Sequence, H. Doyle, M. Oppenheimer, Gordon W. F. Drake Jan 1972

Eigenvalues Of The 2p3pp3 And 2p3dd1,3 Bound States Of The Helium Isoelectronic Sequence, H. Doyle, M. Oppenheimer, Gordon W. F. Drake

Physics Publications

The 1Z expansion method is used to calculate the eigenvalues of the 2p3pP3 and 2p3dD1,3 states of the helium isoelectronic sequence. The results are compared to variational calculations for neutral helium. Wavelengths are predicted for a number of transitions originating in doubly excited states of the heliumlike ions up to Fe xxv. The results for neutral helium are compared to recent beam-foil experiments and alternative line identifications are made. The predicted wavelength for the 2p3dD3-2p2P3 transition is 3014, in close agreement with the line observed by Berry et al. at 3012 ± 2. © 1972 The American Physical Society.

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Relativistic Corrections To Radiative Transition Probabilities, Gordon W. F. Drake Jan 1972

Relativistic Corrections To Radiative Transition Probabilities, Gordon W. F. Drake

Physics Publications

The rate of spontaneous emission of radiation by a loosely bound composite system is calculated from quantum electrodynamics correct through terms of relative order α2Z2. Recent criticisms by Feinberg and Sucher of the semiclassical method of deriving the higher-order radiation coupling terms are discussed. It is proved that the Breit interaction remains valid in the presence of radiation emission and that the semiclassical and quantum-electrodynamic methods of deriving the higher-order coupling terms always yield the same results to relative order α2Z2. We discuss in particular relativistic corrections to allowed and spin-forbidden electric dipole transitions and the 1s2s S13-1s2 S01 magnetic …

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Radiative Transition Rates From The 2p3p P3 And 2p3d D1,3 States Of The Helium Isoelectronic Sequence, Gordon W. F. Drake Jan 1972

Radiative Transition Rates From The 2p3p P3 And 2p3d D1,3 States Of The Helium Isoelectronic Sequence, Gordon W. F. Drake

Physics Publications

The Hylleraas-Scherr-Knight variation-perturbation method is applied to the calculation of oscillator strengths for the dominant transitions from the metastable 2p3p P3 and 2p3d D1,3 states of helium and the heliumlike ions. The results explain the absence of the 1s2pP3-2p3pP3 transition of He i from recent beam-foil excitation spectra. © 1972 The American Physical Society.

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Theory Of Relativistic Magnetic Dipole Transitions: Lifetime Of The Metastable 2s3 State Of The Heliumlike Ions, Gordon W. F. Drake Jan 1971

Theory Of Relativistic Magnetic Dipole Transitions: Lifetime Of The Metastable 2s3 State Of The Heliumlike Ions, Gordon W. F. Drake

Physics Publications

It has recently been established that the radiative lifetime of the metastable 2S3 state of helium and the heliumlike ions is determined by single-photon magnetic dipole (M1) transitions to the ground state, rather than the two-photon process proposed by Breit and Teller. The theory of nl-n′l M1 transitions with n ′ is developed in the Pauli approximation and extended to two-electron systems. Terms arising from relativistic energy corrections and finite-wavelength effects are included. The results for hydrogenic systems are shown to be identical to those obtained in the relativistic four-component Dirac formulation. The coefficients in the Z-1 perturbation expansion of …

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2p2 P3 And 2p3p P1 States Of The Helium Isoelectronic Sequence, Gordon W. F. Drake, A. Dalgarno Jan 1970

2p2 P3 And 2p3p P1 States Of The Helium Isoelectronic Sequence, Gordon W. F. Drake, A. Dalgarno

Physics Publications

Accurate eigenvalues and radiative lifetimes are obtained for the bound 2p2 P3 and 2p3p P1 states of the heliumlike ions He i to Ne ix. A high-order Z-expansion perturbation procedure is used that does not require the explicit solution of perturbation equations. The results are compared with variational calculations. The predicted wavelengths of the 1s2pP3-2p2 P3 and 1s3pP1-2p3pP1 transitions in helium are, respectively, 320.31 and 308.97 Å. Lines have been observed in helium at 320.39 and 309.04 Å. © 1970 The American Physical Society.

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Two-Photon Decay Of The Singlet And Triplet Metastable States Of Helium-Like Ions, Gordon W. F. Drake, G. A. Victor, A. Dalgarno Jan 1969

Two-Photon Decay Of The Singlet And Triplet Metastable States Of Helium-Like Ions, Gordon W. F. Drake, G. A. Victor, A. Dalgarno

Physics Publications

The two-photon decay rates and photon energy distributions of the metastable 2S1 and 2S3 states of the helium isoelectronic sequence are calculated by variational procedures for the ions He i through Ne ix. © 1969 The American Physical Society.

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Singlet-Triplet Mixing In The Helium Sequence, Gordon W. F. Drake Jan 1969

Singlet-Triplet Mixing In The Helium Sequence, Gordon W. F. Drake

Physics Publications

Accurate variational calculations are presented for the off-diagonal matrix elements of the Breit interaction between the 2P1 and 2P3 states of several members of the helium iso-electronic sequence. A comparison is made with recent Z-expansion calculations, which are accurate through terms of order α2Z3. The comparison shows that the Z-expansion method for off-diagonal mixing is potentially useful in the theory of many-electron atoms. The effect of singlet-triplet mixing on the 2P3 excitation cross sections is briefly discussed. © 1969 The American Physical Society.

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Nonadiabatic Long-Range Forces, A. Dalgarno, Gordon W. F. Drake, G. A. Victor Jan 1968

Nonadiabatic Long-Range Forces, A. Dalgarno, Gordon W. F. Drake, G. A. Victor

Physics Publications

A general expression is obtained for the leading long-range correction to the static interaction of a slowly moving charged or neutral system at a large distance from a spherically symmetric atom, and precise estimates are presented of the magnitude for the systems H, HeA (1S1,2S1,A and A 2S3), Ne, Ar, Kr, Xe, Li+A (1S1,2S1,A and A 2S3), Li, Na, K, Rb, Cs, H2, N2, and CH4. © 1968 The American Physical Society.

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