Coherent excitation of the singlet-triplet mixed<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>1</mml:mn><mml:mi>s</mml:mi><mml:mn>4</mml:mn><mml:mi>f</mml:mi></mml:math>state of helium

Wang, Jingbo; Williams, James; Stelbovics, A. T.; Furst, John; Madison, Don H.

doi:10.1103/physreva.52.2885

Cited by 17 publications

(8 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The principle can be extended to higher-order coincidence measurements for higher angular momentum states. A feasibility study for the 4f states of helium is being considered [15].…”

mentioning

confidence: 99%

Complete Determination of Excitation Amplitudes and Phases for the31DState of Helium

1997

Self Cite

View full text Add to dashboard Cite

Observations of triple coincidence polarization correlations of the sequential cascading photons (667.8 nm 3 1 D ! 2 1 P and 58.4 nm 2 1 P ! 1 1 S transitions) and the scattered electrons from electron impact excitation of the 3 1 D state of helium have determined the amplitudes and relative phases of the magnetic substates. The ambiguity of electron-photon coincidence measurements, which determine only the cosine of the sum of the phases between the m 62 amplitudes, is resolved. The measured amplitudes and phases at 60 eV incident energy and 40 ± scattering angle confirm the convergent close coupling values. [S0031-9007 (97)04277-4] PACS numbers: 34.80.DpFundamental studies of quantum physics frequently concern the symmetry and invariances of dynamical systems. The continuous symmetries of space, time, and rotation lead to the conservation of linear momentum, energy, and angular momentum which lead to the well known structure of atoms and their associated scattering properties. The reflection and rotational symmetries of an electronic charge distribution for a specific electronically excited state of an atom are revealed by choosing a reference axis or frame and determining the state multipoles. For example, the selection of an axis of cylindrical symmetry and detection of a nonisotropic population of the radiated photons determines the polarization of the atomic state. The selection of planar symmetry and detection of the radiated photons in coincidence with the scattered electron leads generally to knowledge of the atomic alignment and orientation. The alignment is defined as the nonisotropic population of magnetic substates of equal M with ͗M͘ 6͗J 2 ͘͞3 and determines the shape and size of the electronic charge cloud. The orientation is defined as the nonisotropic population of the 1M and 2M magnetic substates and determines the angular momentum transferred during the excitation process. Work of this type has been reviewed [1,2] and forms part of the quest for quantum mechanically complete measurements [1][2][3][4][5] to determine the scattering amplitudes and relative phases for a unique state and specific scattering dynamics.Studies of the 2 1 P state characterization with the detection of two particles (the scattered electron and the single 2 1 P to 1 1 S photon) are extensive and essentially complete [2]. However, the complete characterization of the amplitudes and relative phases for higher angular momentum states requires a lowering of the scattering symmetry and hence the detection of an increasing number of photons. For the 3 1 D state of helium studied here, the polarization requires specification of only an axis of symmetry and has been measured frequently since about 1964 [6]. However, angular and polarization correlation analyses, requiring a plane of symmetry and hence the detection of two outgoing particles (the scattered energy loss electron and either the 3 1 D to 2 1 P or 2 1 P to 1 1 S photon), have been made only since about 1987 [7][8][9][10]. Similar measurements of the correlations of th...

show abstract

“…The principle can be extended to higher-order coincidence measurements for higher angular momentum states. A feasibility study for the 4f states of helium is being considered [15].…”

mentioning

confidence: 99%

Complete Determination of Excitation Amplitudes and Phases for the31DState of Helium

1997

Self Cite

View full text Add to dashboard Cite

show abstract

“…D state obtained from the triple coincidence observation of the scattered energy loss electron and the two sequential cascading photons. In the experimental setup, where the first photon polarisation and the second photon intensity (without polarisation) were measured in coincidence, the Stokes parameters are given by, (21) (1)…”

Section: The Helium 3*d State and Complete Experimentsmentioning

confidence: 99%

Quantum mechanically complete measurements in electron impact excitation of helium

Mikosza¹

2000

AIP Conference Proceedings

View full text Add to dashboard Cite

A complete quantum description of the 3 ! D state of helium, that is the amplitudes and relative phases for the m = 0, ±2 magnetic sublevels are reported. All state multipoles (T(2) kq) (k = 0-4, k>q>-k) that describe the population and the anisotropy of the excited He(3 1 D) state are presented. The data were determined for 60eV incident electrons and 40°e lectron scattering angle. The experimental procedure was to measure the triple-coincidence, polarisation correlations of the sequential cascading photons (667.8 nm 3 ] D->2'P and 58.4 nm 2 1 P-»1 1 S transitions) and the scattered n = 3 energy loss electrons. Simultaneous measurements of the three twoparticle coincidence pairs determined accurate magnitudes of the scattering amplitudes and phases as well as enabling consistency checks with earlier data. The triple coincidence data determined the sign of the relative m = ±2 phases. The results are presented in a simplifying diagrammatic form. As yet there are no other complete experimental determinations of the 3 ! D state. The measurements are in agreement, within the experimental uncertainty, with the Convergent Close Coupling (CCC) calculations. Previous data for helium at 40eV incident electrons are discussed in the context of the present triple-coincidence results. The desirability of a recently introduced parameter notation for the helium 3 1)3 D states is questioned with respect to physical insight.

show abstract

“…The basic theoretical framework was established earlier and reported in Wang et al (1995). For clarity, a brief discussion and the relevant results are given here.…”

Section: Theorymentioning

confidence: 99%