Mean Lives of the 2p, 3p, 4p, 5p, and 6p2PLevels in He II

Lundin, L.; Oona, H.; Bickel, William S.; Martinson, I.

doi:10.1088/0031-8949/2/4-5/014

Cited by 12 publications

(2 citation statements)

References 9 publications

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“…Our improved lifetime measurement is considerably more accurate than the beam-foil result of (0.98+0.05)X10 ' s by Lundin et al [14] and our own previous measurement of (0.9992+0.0026) X10 ' s. It confirms basic radiation theory at the 0.075% level of accuracy for a fundamental one-electron atomic system. Thus the source of the discrepancy of several standard deviations between theory and experiment for the +0.…”

Section: Solid-angle Correctionsupporting

confidence: 84%

He+2pstate lifetime by a quenching-asymmetry measurement

1992

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An interference asymmetry in the angular distribution of the Ly-a quenching radiation emitted by He ions in the metastable 2s&/2 state is measured to high precision to obtain the lifetime of the 2p, /, state. The derived lifetime of (0.997 17+0.00075) X 10 ' s is the most accurate available for a fundamental atomic system. A detailed discussion of systematic corrections is included. The result is in good agreement with theory, thereby confirming the theory of radiative transition probabilities to 0.075%%uo, and indicating that differences between theory and experiment for the alkali metals must be due to either inadequate wave functions or experimental errors.PACS number(s): 32.70.Fw for spontaneous magnetic dipole (Ml) transitions from the 2s&/2 to the ls, /2 ground state and for magnetic quadrupole (M2) transitions via the 2p3/2 state. To lowest order in the field strength F= lEl, the various amplitudes are given in terms of reduced matrix elements by 46113

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Section: Solid-angle Correctionsupporting

confidence: 84%

He+2pstate lifetime by a quenching-asymmetry measurement

1992

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“…A very accurate measurement of the 2p lifetime is reported by Drake et al [27], and for the other lifetimes we have taken the lifetimes of the corresponding states in H adjusted for the helium ion [28]. Experimental values for some of the He + lifetimes are also available from beam-foil spectroscopy experiments [29,30] and for the 2s state from a decay-in-flight experiment [31]. The individual contributions from the four separate states are plotted as thin solid curves in figure 3.…”

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confidence: 99%

Doubly excited states of helium observed inN- andl-specific partial photoionization cross-sections using lifetime-resolved fluorescence spectroscopy

Harries

Sullivan

Obara

et al. 2003

J. Phys. B: At. Mol. Opt. Phys.

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We have used a lifetime-resolved fluorescence technique to obtain the first measurements of partial photoionization cross-sections of ground state neutral helium with both N-and l-specific final ion state separation. Structure is observed in the He 4lnl doubly excited state regions and the resulting resonance profiles and energy positions qualitatively compared to previously reported theoretical calculations. Due to the sensitive nature of the N-and l-specific partial cross-sections, states from the (4, −2) n series are observed for the first time.The doubly excited states of helium have long been of interest since the first observations [1, 2] both experimentally and theoretically, particularly since becoming accessible to study in tunable photoexcitation with the advent of synchrotron radiation sources in the 1960s [3]. Most recently there have been very high resolution experimental studies of the doubly excited states observed in total ion yield [4-6] and fluorescence photon and metastable singly excited atom yield [7-10] and their photoexcitation and subsequent decay has also been investigated in an electric field [11]. A review of theoretical results is given by Tanner et al [12]. Most of the recent studies have concentrated on the states in Rydberg series which converge on the 'N = 2' threshold, i.e. the threshold above which photoionization can produce He + in an excited state. There are 2N −1 'optically allowed' 1 P o series converging on each excited ion threshold of ion state principal quantum number N, and for the lowest N = 2 threshold all of these have been observed in photoion yield, VUV photon yield and metastable yield. Ultrahigh resolution measurements [9,10] have also recently revealed the importance of triplet states. States converging on higher thresholds are more difficult to study since there are a larger number of 3 Author to whom any correspondence should be addressed.

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Anisotropies and Lamb Shifts in Hydrogenicions Ions: Twenty Years of Progress

Drake

Wijngaarden

1996

Selected Topics on Electron Physics

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Mean Lives of the 2p, 3p, 4p, 5p, and 6p²PLevels in He II

Cited by 12 publications

References 9 publications

He+2pstate lifetime by a quenching-asymmetry measurement

He+2pstate lifetime by a quenching-asymmetry measurement

Doubly excited states of helium observed inN- andl-specific partial photoionization cross-sections using lifetime-resolved fluorescence spectroscopy

Anisotropies and Lamb Shifts in Hydrogenicions Ions: Twenty Years of Progress

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