Multipole rate coefficients for collisional excitation of Fe XIII by isotropic electrons

The European Physical Journal D - In the present work, we describe a new method, dressed cross-section model (DCSM), enabling implementation of large number of atomic transitions (~106 and more) in...     

Theory and physical importance of integrated state multipoles

We consider the polarisation properties of light emitted by heavy atoms after excitation by polarised electrons. It is discussed what information on spin-dependent forces can be obtained from the measurements.     

Multipole cross sections for collisional excitation of highly charged ions by isotropic electrons

The relativistic distorted-wave program of the flexible atomic code for calculating the cross sections for electron-impact excitation of ions between fine-structure levels is extended to get the multipole components of cross sections in the case of excitation by isotropic electrons. These components may be needed for interpreting the intensity and polarization of line emissions from thermal plasmas exposed to anisotropic radiations, such as the solar corona under photosphere irradiation. Illustrative numerical results are given for excitation of Si-like Fe¹²⁺ between the , and levels. These results can be useful in the analysis of infrared forbidden lines emitted from the solar corona. A comparison is made with the only published work based on the semi-relativistic distorted-wave approximation, showing some agreement for the excitation and discrepancies for the weak transition .     

Angular distribution of electrons during two-photon ionization of atoms by elliptically polarized radiation

Two-photon ionization of the hydrogen-like uranium ion by elliptically polarized radiation is investigated in the present work. It is demonstrated that the fundamental effect of interference of the probability amplitudes arises in the angular photoelectron distribution when the degree of ellipticity of ionizing radiation is varied. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 39–41, December, 2008.     

Polarization detection of trapped electrons via interaction with polarized atoms

Electrons were trapped in an electrostatic quadrupole trap with superimposed homogeneous magnetic field. The electrons were polarized by spin exchange with a polarized atomic beam. The free trapped electron polarization was converted to a change in the electron translational energy via spin-dependent inelastic collisions with the atomic beam, and the electron translational temperature was monitored. Discussed are the development of this variation of the measurement technique, characteristics of electron storage, and the electron-polarized atom inelastic interaction as a function of electron temperature and time. The method has been applied to the detection of the (g-2) resonance of free, stored electrons.     

Electron exchange in dissociative excitation of molecular hydrogen using polarized electrons

The effects of electron exchange and spin orbit interaction in dissociative excitation processes in H2 molecules have been explored using excitation by polarized electrons. Observations of the circular and linear Stokes polarizations of the Balmer-alpha photons determined the alignment and orientation of the excited atomic hydrogen atoms, the excited molecular states, and the dissociative excitation processes via predissociation with short and long range transitions.     

NaK分子激发态的预离解和碰撞激发转移

用Ar+激光器固定频率488.0nm线激发Na-K混合蒸汽,NaK分子激发态通过自发辐射、预离解和与基态原子的碰撞激发转移而去布居,测量在不同K原子密度下原子荧光对分子荧光的强度比,结合NaK(E)态寿命,得到了预离解率和碰撞激发转移率.     

Scattering of electrons by atoms

The theoretical procedures of current interest in the calculation of electron atom scattering are discussed with emphasis on the intermediate energy range. The essential features of the mathematical methods are described. Some specific results are compared with experiment to illustrate the accomplishments and the limitations of the theory.     

Elastic scattering of electrons by hydrogen atoms in the (2p) state

Conclusion Since our results are the first set of results in this field, their accuracy can be judged when further results through other methods and through experiment are available.The author is grateful to Dr. J. N. Das for his constant help and encouragement in the preparation of this paper. The numerical results reported in this paper have been calculated on the IBM 1130 at Calcutta University.     

Rydberg state ionization by half-cycle-pulse excitation: strong kicks create slow electrons

The asymptotic velocity distribution of electrons ionized in half-cycle-pulse excitation of high Rydberg states (n=34), placed in a static electric field, is studied using electron velocity-map imaging. At weak half-cycle pulse strengths, the electrons escape over the saddle point in the potential. For strong half-cycle pulses, the electrons are emitted in the direction of the field kick. The much slower and less intense half cycle of opposite polarity, which necessarily follows the main half-cycle pulse, strongly affects the momentum distribution and reduces the excess energy of the electrons significantly.     

Energy spectrum of ejected electrons in ionization of hydrogen atoms by electrons

Energy spectrum of ejected electrons in ionization of hydrogen atoms has been calculated following a multiple scattering theory of Das and Seal [15]. The results show peaks around two to three Rydbergs of energies of the ejected electrons, for incident electron energy of 250 eV and 500 eV, considered here, and for different combinations of the angular variables of the scattered and the ejected electrons, for scattering in a plane. The peaks are very similar to those observed in relativistic K-shell ionization of Ag atoms by electrons at 500 KeV energy [6]. The physical origin of these peaks may be traced to the second order scatterings, scattering first by the atomic nucleus (or the atomic electron) and then a second time by the atomic electron. These peaks are, however, absent in the first Born results. Experimental verification of the present results and theoretical calculation by some other well-known methods will be interesting.     

Elastic scattering of electrons by argon atoms

The partial wave method with a central potential has been applied to investigate the elastic scattering of electrons by the argon atoms in the intermediate energy range (100 eV − 1 keV). The central potential includes the effects of the static field, exchange and polarization. The results are in good accord with recent experimental data. A brief account of this investigation was presented at the X Int. Conf. on the Physics of Electronic and Atomic Collisions held at Paris in July 1977.     

Nuclear excitation by electrons and positrons

Existing measurements of the ratio $\text{σ}{}^{\mathrm{?}}\text{σ}{}^{\mathrm{+}}$, the nuclear excitation cross sections produced by electrons and positrons, are compared with the results of distorted wave calculations. The behaviour as a function of atomic number Z and electron energy E₀ is shown to be principally due to Coulomb distortion. The value of $\text{σ}{}^{\mathrm{?}}\text{σ}{}^{\mathrm{+}}$ displays no clear structure corresponding to resonances in the photoabsorption cross section, except that it should be quite sensitive to the presence of quadrupole strength.     

L-shell ionization of atoms by relativistic electrons

A theoretical study of theL-shell ionization of atoms by relativistic electrons is made for atomic numbers in the range 47 to 92. A new potential model recently proposed by Das and Chakraborty dealing with atomic screening effect in a better way has been used. The results are in satisfactory agreement when compared with some available experimental results and also with the theoretical results of Scofield.