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Zeitschrift für Naturforschung A

Einfluß eines homogenen Magnetfeldes auf die Polarisation von Fluoreszenzlinien des Cu I-Spektrums nach Elektron enstoßanregung/ Influence of a homogeneous magnetic field on the polarization of fluorescence lines of the Cu I-spectrum induced by electron bombardment

G. Anger, Michael v. Hartrott, H.‐U. Martyn, Gebhard von Oppen

Published Nov 1, 1970• 2 citations
Publisher

Abstract

Abstract Using atomic beam techniques the polarization of fluorescence lines of the Cu I-spectrum was measured in dependence on magnetic field strength. The Cu-atoms were excited by electron bombardment and the magnetic field was parallel to the electron beam. Due to the decoupling of the hyperfinestructure of excited levels of the Cu I-spectrum the polarization of some observed spectral lines [3247 Å (4p 2P3/2 -4s 2S1/2); 5153 Å (4d 2D3/2 -4p 2P1/2); 5218 Å (4d2D5/2 - 4p 2P3/2)] increases with increasing magnetic field strength. These polarization measurements, which correspond to investigations on resonance scattering of light done by HEYDENBURG et al., can be used for a determination of hfs-coupling constants of excited states. The measurements on the 3247 Å-resonance line are used for a comparison with results of accurate level-crossing-experiments. Satisfactory agreement is obtained. The discussion of the polarization of the 5153 Å-line yields an A-factor of (9.6 ± 1-0) MHz and a lifetime of τ ≈1.7 · 10 -8 sec for the 4d2D3/2-level.

DOI
10.1515/zna-1970-1101

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Abstract Using separated isotopes the hyperfine structure of the 5p 2P3/2-state in Ag I-spectrum was investigated by scattering the resonance line on an atomic beam in parallel magnetic and electric fields. With the theoretical positive sign of the Stark-constant β, the shift of the Heydenburg- and level-crossing-signals with electric fields can be explained by the following parameters: Ag (107) : A = - (32,4 ± 0.5) Mc/sec , Ag (109): A - - (37,3 ± 0.8) Mc/sec , β (2P3/2) = (5.15 ± 0.15) (kc/sec) (kV/cm) -2 , τ (2p3/2) = (6.3 ± 0.6 ) · 10-9 sec.

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On the excitation of polarised light by electron impact. II.—Mercury

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The theory of how excited-state hyperfine structure can be determined using a magnetic field to decouple the nuclear and electronic angular momentum is presented. The initial excited state is assumed to have an anisotropic Zeeman sublevel population distribution, which can be conveniently created by a laser-induced multiphoton excitation of an unpolarized atom. The Zeeman sublevel populations are subsequently mixed by the hyperfine interaction. The degree of mixing is controlled by a magnetic field applied along the quantization axis. The relative Zeeman sublevel populations can be monitored by detecting the polarization of fluorescence emitted when the excited state radiatively decays. It is convenient to take the ratio of two time-integrated fluorescent signals measured for orthogonal linear polarizations, since this is independent of the excited-state number density. The plot of this ratio versus magnetic field is very well approximated by a Lorentzian curve whose half-width is proportional to the magnetic dipole hyperfine coupling constant. This method was used to determine the magnitude of the magnetic dipole constant of the cesium 8${\mathit{D}}_{3/2}$ state to be 3.92\ifmmode\pm\else\textpm\fi{}0.10 MHz, which is in excellent agreement with previous results.

Physical Review A•Mar 1, 1991•6 citations
Abstract Using atomic beam techniques the polarization of fluorescence lines of the Cu I-spectrum was measured in dependence on magnetic field strength. The Cu-atoms were excited by electron bombardment and the magnetic field was parallel to the electron beam. Due to the decoupling of the hyperfinestructure of excited levels of the Cu I-spectrum the polarization of some observed spectral lines [3247 Å (4p 2P3/2 -4s 2S1/2); 5153 Å (4d 2D3/2 -4p 2P1/2); 5218 Å (4d2D5/2 - 4p 2P3/2)] increases with increasing magnetic field strength. These polarization measurements, which correspond to investigations on resonance scattering of light done by HEYDENBURG et al., can be used for a determination of hfs-coupling constants of excited states. The measurements on the 3247 Å-resonance line are used for a comparison with results of accurate level-crossing-experiments. Satisfactory agreement is obtained. The discussion of the polarization of the 5153 Å-line yields an A-factor of (9.6 ± 1-0) MHz and a lifetime of τ ≈1.7 · 10 -8 sec for the 4d2D3/2-level.
Abstract Using separated isotopes the hyperfine structure of the 5p 2P3/2-state in Ag I-spectrum was investigated by scattering the resonance line on an atomic beam in parallel magnetic and electric fields. With the theoretical positive sign of the Stark-constant β, the shift of the Heydenburg- and level-crossing-signals with electric fields can be explained by the following parameters: Ag (107) : A = - (32,4 ± 0.5) Mc/sec , Ag (109): A - - (37,3 ± 0.8) Mc/sec , β (2P3/2) = (5.15 ± 0.15) (kc/sec) (kV/cm) -2 , τ (2p3/2) = (6.3 ± 0.6 ) · 10-9 sec.
Abstract In a number of recent papers descriptions have been given of how the light from atoms excited by a directed stream of electrons is polarised, in the absence of any external field of force. In particular we may refer to the paper by one of the present writers (Paper I), where some of the characteristics of the effect in mercury were discussed. It was found that the different lines of the spectrum were differently polarised, both in magnitude and direction. The behaviour of the polarisation when a magnetic field is applied to the mercury atoms was found to be identical with the effect produced by a similar field on the polarisa­tion when the light is excited by the absorption of plane polarised light, the electric vector of which is parallel to the direction of the stream of electrons. In this way, the polarisation of the light excited by electron impact was shown to be closely related to the polarisation of resonance radiation, which had been investigated by Wood and Ellett and others. In the paper referred to, the measurement of the polarisation of the spectral lines was, except in an individual instance, only qualitative. Since its appearance two papers have appeared in which polarisation measurements of the mercury lines excited by electron impact have appeared. Eldridge and Olsen gave qualitative results, and these confirmed those which we had given. Quarder gives quantitative measure­ments which are also for the most part in general accord. The aim of the present paper is to describe quantitative results, and, as will be seen, these are not in all cases in detailed agreement with those given by Quarder. The second aim is to determine the variation of the polarisation with the velocity of the electron stream, a point which has not been previously attempted. In Paper I it was shown that the magnitude of the polarisation is intimately connected with the dynamics of the collision process. By the electron impact, the atom is raised from its normal state into an upper quantum state, and by its return into the normal state, or into another state, light is emitted. The magnitude of the polarisation depends on both of these processes, but the second process, the actual emission of the light, is well understood. Polarisation measurements therefore give a powerful means of investigating the collision of an electron with an atom in the case when excitation of the atom takes place, and it is in this that their main interest lies.
The polarisation of spectrally resolved Na D lines excited by white, linearly polarised light in a homogeneous magnetic field up to 1000 G was measured by means of the crossed-beam technique. The axis of observation, the sodium beam and the direction of the magnetic field were mutually at right angles. The incoming light beam was directed along the magnetic field and linearly polarised either parallel to the axis of observation or perpendicular to it. A Lyot filter of high transmission and a sensitive photon-counting technique made it possible to detect the small intensities of the resolved Na D doublet excited by the light of a xenon arc lamp. The measured polarisations are found to be in excellent agreement with those calculated by means of Breit's theory and the ambiguities of earlier investigations are completely removed. The importance of our results for electron impact excitation in magnetic fields parallel to the beam is discussed. It is shown that the polarisation of the electron impact excited Na D lines is no longer perturbed by hyperfine structure if a magnetic field of 500 G parallel to the beam is applied.
Abstract In level-crossing experiments on high-velocity atoms, the shape of the observed signals depends sensitively on inhomogeneities of the applied magnetic field. With regard to the interpretation of such signals, we investigated the magnetic-field dependence of He I-fluorescence light excited by He-ion-He-atom collisions. Due to the inhomogeneity of the applied magnetic field, the observed level-crossing signals have a distorted shape with an oscillating structure in the wings. Taking into account the motion of the excited atoms, the shape of the signals will be explained.
The theory of how excited-state hyperfine structure can be determined using a magnetic field to decouple the nuclear and electronic angular momentum is presented. The initial excited state is assumed to have an anisotropic Zeeman sublevel population distribution, which can be conveniently created by a laser-induced multiphoton excitation of an unpolarized atom. The Zeeman sublevel populations are subsequently mixed by the hyperfine interaction. The degree of mixing is controlled by a magnetic field applied along the quantization axis. The relative Zeeman sublevel populations can be monitored by detecting the polarization of fluorescence emitted when the excited state radiatively decays. It is convenient to take the ratio of two time-integrated fluorescent signals measured for orthogonal linear polarizations, since this is independent of the excited-state number density. The plot of this ratio versus magnetic field is very well approximated by a Lorentzian curve whose half-width is proportional to the magnetic dipole hyperfine coupling constant. This method was used to determine the magnitude of the magnetic dipole constant of the cesium 8D3/2{\mathit{D}}_{3/2}D3/2​ state to be 3.92\ifmmode\pm\else\textpm\fi{}0.10 MHz, which is in excellent agreement with previous results.