Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review A

Intensity Fluctuations of Light from Fast H Atoms: Addenda on Initial-State Populations and Cascades

Ivan A. Sellin, P. M. Griffin, John A. Biggerstaff

Published May 1, 1970• 6 citations
Publisher

Abstract

A more extensive analysis of the effects of different assumptions about initial state populations is added to a previous paper on the coherent excitation of hydrogen fine structure by foils. It is found that the previously postulated alignment of angular momenta perpendicular to the beam direction is a sufficient but not necessary assumption; an alternative assumption that the broad $l$-state distribution of the collision products has a maximum for $d$ states also matches the experimental traces adequately. A method of obtaining initial state populations in a manner which suppresses the corrections required for cascade effects is discussed. The method avoids the errors of extrapolating decay-curve fits.

DOI
10.1103/physreva.1.1553

Related papers

Comment on Relative Magnetic Substate Amplitudes in Foil Excitation of Fast Hydrogen Atoms

Ivan A. Sellin

If the particle-foil interaction potential governing production of H atoms coherently excited by passage through thin foils obeys the $\mathrm{LS}$ coupling scheme applied by Macek (conservation of $z$ components of total orbital and spin angular momenta of the entire particle-foil system, and incoherence of final states of foil constituents), the ad hoc assumption that random phases prevail among the hydrogenic magnetic substate amplitudes invoked in the interpretation of certain recent experiments is avoided. Arguments concerning relative phases of states of different orbital angular momentum are unaffected.

Physical Review A•Apr 1, 1971•1 citation

Periodic Intensity Fluctuations of Balmer Lines from Single-Foil Excited Fast Hydrogen Atoms

Ivan A. Sellin, Charles D. Moak, P. M. Griffin +1 more

Protons with velocities ranging from 3.2 \ifmmode\times\else\texttimes\fi{} ${10}^{8}$ to 6.3 \ifmmode\times\else\texttimes\fi{} ${10}^{8}$ cm/sec were passed through a carbon foil producing excited hydrogen atoms which decayed in flight after emergence. With the foil in magnetic fields from 2 to 25 G, the lines ${\mathrm{H}}_{\ensuremath{\alpha}}$ through ${\mathrm{H}}_{\ensuremath{\epsilon}}$ showed periodic intensity fluctuations due to Stark mixings of fine-structure levels caused by motional electric fields (6-158 V/cm). An extension of the Bethe-Lamb theory of Stark quenching provides good agreement between a small number of theoretically dominant frequencies and the measured fluctuation frequencies. Apparent discrepancies between theory and experiment noted by other experimenters are shown to be removed by our calculations except in one measurement on ${\mathrm{Ly}}_{\ensuremath{\alpha}}$. The necessity of using double foils postulated in the previous work is discussed. Our analysis suggests the preferential alignment of the final-state angular momenta perpendicular to the beam direction. Reasons for this alignment are given.

Physical Review•Aug 5, 1969•34 citations

Optical electric resonance investigation of a fast hydrogen beam. I. Theory of the atom-RF field interaction

Mark P. Silverman, F. M. Pipkin

This series of articles will describe a novel method of utilizing optical detection of RF-induced fine structure transitions to investigate the population of excited states of fast hydrogen atoms produced by charge exchange collisions between an initial proton beam and various gas or foil targets. In Part I a model of the charge exchange collision and the interaction of the hydrogen beam with an external oscillatory field are considered within the framework of the density matrix formalism and expressions are obtained for the RF lineshapes in terms of the initial atomic density matrix elements.

Journal of Physics B Atomic and Molecular Physics•Apr 21, 1974•7 citations

Interference of Fine-Structure Levels of He ii

William S. Bickel, STANLEY BASHKIN

Passage of a beam of foil-excited ${\mathrm{He}}^{+}$ ions through a small electric field induced quasiperiodic fluctuations in the intensity of the light emitted from levels $n=7, 8, 9, \mathrm{and} 10$. Both ${\mathrm{He}}^{3}$ and ${\mathrm{He}}^{4}$ beams were used. Only one foil was needed, in contrast to the double-foil arrangement reported necessary for hydrogen. The observations are discussed in terms of Stark-induced interference of the fine-structure levels of He ii, but discrepancies between the data and the calculations are large.

Physical Review•Oct 5, 1967•31 citations

Interference Between Coherent Emissions in the Measurement of Atomic Lifetimes

J. H. Macek

It is pointed out that the (zero-field) oscillations seen in the decay curves for atoms excited by beam-foil collisions may be due to interference of light from different fine-structure levels; the interference can only be seen, however, if light of different polarizations is detected with different sensitivity.

Physical Review Letters•Jul 7, 1969•74 citations

Stark-Induced Quantum Beats in H L Y α Emission

H. J. Andrä

Intensity beats in the emission of $\mathrm{L}{\mathrm{y}}_{\ensuremath{\alpha}}$ from beam-foil excited hydrogen in various static electromagnetic field configurations have been studied. The observed beat frequencies agree with the calculated values, which are independent of the field directions. The beat amplitudes, however, show significant dependence on the field directions relative to the beam. The theory for emission of light from the decay of coherently excited states is applied in the sudden perturbation limit. Agreement with experiment can only be obtained under the assumption that the foil excitation generates initial coherent wave functions ${\ensuremath{\Psi}}_{\mathrm{I},\mathrm{I}\mathrm{I}}=\ensuremath{\alpha}|p,\frac{1}{2},\ifmmode\pm\else\textpm\fi{}\frac{1}{2}〉+\ensuremath{\beta}|s,\frac{1}{2},\ensuremath{\mp}\frac{1}{2}〉$, where $|l,j,{m}_{j}〉$ notation and the beam as quantization axis are used. The ratio $\frac{\ensuremath{\alpha}}{\ensuremath{\beta}}$ is then determined, which gives the ratio of the excitation cross section of the $p$ to that of the $s$ states as $\frac{{\ensuremath{\sigma}}_{p}}{{\ensuremath{\sigma}}_{s}}>~4\ifmmode\pm\else\textpm\fi{}1$ at a beam energy of 200 (keV) per atom.

Physical Review A•Dec 1, 1970•42 citations
A more extensive analysis of the effects of different assumptions about initial state populations is added to a previous paper on the coherent excitation of hydrogen fine structure by foils. It is found that the previously postulated alignment of angular momenta perpendicular to the beam direction is a sufficient but not necessary assumption; an alternative assumption that the broad lll-state distribution of the collision products has a maximum for ddd states also matches the experimental traces adequately. A method of obtaining initial state populations in a manner which suppresses the corrections required for cascade effects is discussed. The method avoids the errors of extrapolating decay-curve fits.
If the particle-foil interaction potential governing production of H atoms coherently excited by passage through thin foils obeys the LS\mathrm{LS}LS coupling scheme applied by Macek (conservation of zzz components of total orbital and spin angular momenta of the entire particle-foil system, and incoherence of final states of foil constituents), the ad hoc assumption that random phases prevail among the hydrogenic magnetic substate amplitudes invoked in the interpretation of certain recent experiments is avoided. Arguments concerning relative phases of states of different orbital angular momentum are unaffected.
Protons with velocities ranging from 3.2 \ifmmode\times\else\texttimes\fi{} 108{10}^{8}108 to 6.3 \ifmmode\times\else\texttimes\fi{} 108{10}^{8}108 cm/sec were passed through a carbon foil producing excited hydrogen atoms which decayed in flight after emergence. With the foil in magnetic fields from 2 to 25 G, the lines ${\mathrm{H}}_{\ensuremath{\alpha}}$ through ${\mathrm{H}}_{\ensuremath{\epsilon}}$ showed periodic intensity fluctuations due to Stark mixings of fine-structure levels caused by motional electric fields (6-158 V/cm). An extension of the Bethe-Lamb theory of Stark quenching provides good agreement between a small number of theoretically dominant frequencies and the measured fluctuation frequencies. Apparent discrepancies between theory and experiment noted by other experimenters are shown to be removed by our calculations except in one measurement on ${\mathrm{Ly}}_{\ensuremath{\alpha}}$. The necessity of using double foils postulated in the previous work is discussed. Our analysis suggests the preferential alignment of the final-state angular momenta perpendicular to the beam direction. Reasons for this alignment are given.
This series of articles will describe a novel method of utilizing optical detection of RF-induced fine structure transitions to investigate the population of excited states of fast hydrogen atoms produced by charge exchange collisions between an initial proton beam and various gas or foil targets. In Part I a model of the charge exchange collision and the interaction of the hydrogen beam with an external oscillatory field are considered within the framework of the density matrix formalism and expressions are obtained for the RF lineshapes in terms of the initial atomic density matrix elements.
Passage of a beam of foil-excited He+{\mathrm{He}}^{+}He+ ions through a small electric field induced quasiperiodic fluctuations in the intensity of the light emitted from levels n=7,8,9,and10n=7, 8, 9, \mathrm{and} 10n=7,8,9,and10. Both He3{\mathrm{He}}^{3}He3 and He4{\mathrm{He}}^{4}He4 beams were used. Only one foil was needed, in contrast to the double-foil arrangement reported necessary for hydrogen. The observations are discussed in terms of Stark-induced interference of the fine-structure levels of He ii, but discrepancies between the data and the calculations are large.
Intensity beats in the emission of $\mathrm{L}{\mathrm{y}}_{\ensuremath{\alpha}}$ from beam-foil excited hydrogen in various static electromagnetic field configurations have been studied. The observed beat frequencies agree with the calculated values, which are independent of the field directions. The beat amplitudes, however, show significant dependence on the field directions relative to the beam. The theory for emission of light from the decay of coherently excited states is applied in the sudden perturbation limit. Agreement with experiment can only be obtained under the assumption that the foil excitation generates initial coherent wave functions ${\ensuremath{\Psi}}_{\mathrm{I},\mathrm{I}\mathrm{I}}=\ensuremath{\alpha}|p,\frac{1}{2},\ifmmode\pm\else\textpm\fi{}\frac{1}{2}〉+\ensuremath{\beta}|s,\frac{1}{2},\ensuremath{\mp}\frac{1}{2}〉$, where ∣l,j,mj〉|l,j,{m}_{j}〉∣l,j,mj​〉 notation and the beam as quantization axis are used. The ratio $\frac{\ensuremath{\alpha}}{\ensuremath{\beta}}$ is then determined, which gives the ratio of the excitation cross section of the ppp to that of the sss states as $\frac{{\ensuremath{\sigma}}_{p}}{{\ensuremath{\sigma}}_{s}}>~4\ifmmode\pm\else\textpm\fi{}1$ at a beam energy of 200 (keV) per atom.