Relative and absolute level populations in beam-foil—excited neutral helium

Davidson, June

doi:10.1103/physreva.12.1350

Cited by 23 publications

(11 citation statements)

References 37 publications

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“…3 represent an average. The scatter of individual data points given in [7] is substantially larger than that of our work (Fig. 1).…”

Section: (1 -And)pacontrasting

confidence: 60%

“…In Ref. [7] are given population curves for six He Ia levels; the open circles given in Fig. 3 represent an average.…”

Section: (1 -And)pamentioning

confidence: 99%

“…Recently, Davidson has performed a determination of absolute level populations in He I" at a projectile energy of 275 keV [7], for levels with principal quantum number n ranging from 3 to 6. Her relative numbers agree very well with those of Andersen et al…”

Section: Comparison To Absolute Beam-foil Excitation Datamentioning

confidence: 99%

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Tracking Simulation of the Ions Trapped in the Nonlinear Field of Electron Beams in Storage Rings

Miyahara¹

1996

Jpn. J. Appl. Phys.

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A study of the beam-foil excitation mechanism using 30-300 keV He+ projectiles. B. Dynefors,l I.Beam-foil excitation functions have been measured for some optical transitions in neutral He (singly as well as doubly excited) and ionized He in the projectile energy range 30-300 keV. The excitation functions have been converted into relative population functions, which for levels within individual level schemes are proportional. The three sets of population functions have been linked by two parameters, one accounting for Rydberg states, and the other accounting for Is core vacancies. The two empirically determined parameters reproduce also charge state distribution data as well as an absolute beam-foil population measurement.The relative level populations have been measured for the nd 3D Rydberg series, n < 11, at 100 keV and at 200 keV and found to be asymptotically close to an r3 behaviour.A search for optical observation of radiative electron capture was performed at 100 keV and 200 keV, the result being negative.

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“…3 represent an average. The scatter of individual data points given in [7] is substantially larger than that of our work (Fig. 1).…”

Section: (1 -And)pacontrasting

confidence: 60%

“…In Ref. [7] are given population curves for six He Ia levels; the open circles given in Fig. 3 represent an average.…”

Section: (1 -And)pamentioning

confidence: 99%

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Tracking Simulation of the Ions Trapped in the Nonlinear Field of Electron Beams in Storage Rings

Miyahara¹

1996

Jpn. J. Appl. Phys.

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“…One example was a two exponential sum with both coefficients and both meanlives as free fitting parameters. Another example was a nine exponential sum with two coefficients and one meanlife free, and the other meanlives fixed to theoretical values of likely cascades with coefficients as suggested by the He I excited state population studies of Davidson [11]. Several other fitting functions were also tested, but the primary lifetime extracted was remarkably insensitive to the form of the mathematical function used to account for cascades.…”

Section: Data Treatmentmentioning

confidence: 98%

A high precision beam-foil meanlife measurement of the 1s 3p 1 P level in He I

et al. 1976

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A beam-foil measurement of the meanlife of the i s 3p 1p level in He I has been made and yields the value 1.7225 +0.0046 ns. The measurement was made with standard beam-foil techniques and equipment, but special attention was devoted to minimizing sources of uncertainty. The precision far exceeds that of previous beam-foil meanlife measurements and demonstrates that the beam-foil technique is capable of high precision and is competitive with and more flexible than methods such as resonant laser excitation.

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“…with [8,9], b) that ground states with non-zero orbital angular momentum are also highly oriented and c) that the surface scattered beam of light ions consists at 300 keV mainly of neutral and singly charged fractions as can be deduced from the spectra emitted by such scattered beams. Thus we choose 14N+-and 13C+-ions for our experiments which do have L # 0-ground states except for the NIground state.…”

mentioning

confidence: 99%

Nuclear spin polarization produced by ion-beam-surface-interaction, its optical detection and use in an atomic quantum-beat experiment

et al. 1977

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It is shown that nuclear spin polarized ion beams can be generated by ion beam surface interaction at grazing incidence. An optical detection method for the nuclear polarization after foil excitation of such beams is described and used for a hyperfine structure quantum-beat measurement on the 14N II-2 p 3 p 3D-state.In a recent letter [1] it was shown that large Ar + excited state orientations are obtained by 300 keV Ar § ion beam surface interaction at grazing incidence (IBSIGI). Further studies [2] with different ions than Ar § have shown this to be a general phenomenon based on a strong orbital angular momentum orientation due to the anisotropic Coulomb interaction with the surface. These findings make it worth considering the partial transfer of electronic orientation to atomic nuclei with I + 0 via hyperfine interaction in order to generate nuclear spin polarized ion beams for the use in various fields of physics. In this communication we first give theoretical estimates for the nuclear orientations to be expected after I~N+-and 13C+-IBSIGI. We then describe and use a method of optical detection of the nuclear orientation of 13C+-and ~4N+-beams after reexcitation of these beams by a carbon foil at normal incidence. Finally we make use of such a nuclear spin polarized beam in a quantum beat experiment 1-3] on the hyperfine structure of an excited ~4N+-state. According to Reference 1 the IBSIGI generates an initial oriented orbital angular momentum (-Lx) +0 with the right handed coordinate system used in Fig. 1. In ((LS)JI)F-coupling the partial transfer of orientation from this (-Lx) to the nucleus can then be described in three steps: 1) An isotropic electronic spin S and an isotropic nuclear spin I have to be coupled with this (-Lx) to form the eigenstates of the free ion in the ((LS)JI)FM-base.2) The actual transfer takes place as a function of time after the excitation (orientation) process under the combined influence of the fine-and hyperfine interaction. 3) As a result one obtains after averaging over long times compared to the hyperfine periods an orientation (-Ix) which can be calculated by decoupling the system again to the (LMLSMsIMI)-base in order to evaluate the expectation value (-Ix). We choose for the description of the whole procedure the density matrix with its expansion coefficients p(k) with respect to irreducible tensor operators Tq (k~. Taking the reflection symmetry of the IBSIGI with respect to the y-z plane in Fig. 1 into account and choosing the x-axis as quantization axis, only the components Cp (o~ , Lp(ol) , Lp(02) , La(2) P_+2 "" can occur [4] where the k = 0, 1, 2 components characterize the population (monopole-polarization), the orientation (dipole-polarization) and the alignment (quadrupole-polarization), respectively. Since furthermore without external fields k remains a constant of motion during the whole transfer process, we neglect as an approximation the higher multipole polarization components with k>2 and concentrate for sim-

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Relative and absolute level populations in beam-foil—excited neutral helium

Cited by 23 publications

References 37 publications

Tracking Simulation of the Ions Trapped in the Nonlinear Field of Electron Beams in Storage Rings

Tracking Simulation of the Ions Trapped in the Nonlinear Field of Electron Beams in Storage Rings

A high precision beam-foil meanlife measurement of the 1s 3p 1 P level in He I

Nuclear spin polarization produced by ion-beam-surface-interaction, its optical detection and use in an atomic quantum-beat experiment

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