The atom as microscopic undulator

Abstract

Electrons emit electromagnetic radiation when they are accelerated. When an electron moves through a macroscopic magnetic field the acceleration is caused by the Lorentz force and the radiation is called synchrotron radiation. If, on the other hand, the electron is accelerated by the microscopic Coulomb (electric) field of a nucleus, the associated radiation is called bremsstrahlung. In general both types of radiation are incoherent.

In-plane polarisation correlation study of the 31 D state of helium excited by 40 eV electrons

“…The identical preparation of excited states from an initially pure state in these experiments, with conservation of reflection symmetry about the scattering plane, leads to a state which can be described by a single state vector [20) +a_2(O,E) 12-2 ) (1) where aM(O, E) are the angle and energy dependent scattering amplitudes associated with the excited [LM) states. The a ± ~ associated with the 12 ± 1) states are zero because these states have negative reflection symmetry about the scattering plane.…”

“…In this report we are interested in the latter case. van Linden van den Heuvell et al [1,2] discussed the theory of Dstate correlation studies in helium and performed a novel scattered electron-cascade photon angular correlation experiment. However, substantial quantitative studies of 3 1D excitation were first reported by Beijers et al [3] using the polarisation correlation technique in which the linear and circular polarisations of the emitted (31D -21p) dipole radiation were determined.…”

Excitation of He(31 D) by electron impact

“…Previous attempts to investigate the polarization properties of the *On leave from: Fakult~it ffir Physik, Universit/it BieIefeld, D-33501 Bielefeld, Germany emitted light during the decay of collisionally excited He (3 1D) states have mostly been restricted to measurements [5][6][7][8][9] perpendicular to the scattering plane which is defined by the directions of the incoming and outgoing electron. The information obtained from such measurements yielding the so-called Stokes parameters Pi (i = 1-3) is, however, incomplete and at least one more (in-plane) measurement (P4) is needed to extract the full information accessible by such measurements.…”

Phase-Dependent Electron-Ion Recombination in a Microwave Field

“…The essential physics behind such phenomena is often described by the classical simpleman's model, in which the electron is assumed to be created in a flat potential and gains energy from or loses it to the low frequency field. The simpleman's model was originally developed to describe above threshold ionization (ATI) [4][5][6], and it is an excellent approximation in cases in which there is high frequency excitation far above the ionization limit or very strong low frequency fields [1,[7][8][9]. In these terms the excitation of He occurs at an IR phase such that the He electron gains energy from the IR field.…”