Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review

Polarized Resonance Radiation in Weak Magnetic Fields

Robert Williams Wood, A. Ellett

Published Sep 1, 1924• 74 citations
Publisher

Abstract

Effect of a magnetic field on the polarization of resonance radiation of mercury and of sodium.---(1) Mercury $\ensuremath{\lambda}2536$. A beam of plane polarized monochromatic light was focussed on the bulb containing the vapor at low pressure (0\ifmmode^\circ\else\textdegree\fi{}C), and the polarization of the resonance radiation was determined photographically with the aid of a quartz wedge and a double image quartz prism. If the exciting beam is going east with the electric vector vertical, when the earth's field is carefully neutralized the polarization is 90 per cent in any horizontal direction and zero vertically; a field of only 2 gauss directed north reduces the polarization in its direction to nearly zero (the decrease with increasing field being exponential), changes the polarization east and also up to 60 percent, and increases the intensity directed upwards threefold. Similar effects are produced by fields in other directions. The polarization with zero field does not approach 100 per cent at low pressures, since 90 per cent was found also with the vapor at -50\ifmmode^\circ\else\textdegree\fi{}C, when the radiation first appeared. It was thought that the high value might be due to an orientation of the resonating atom by the field of the exciting light, but a beam of concentrated sunlight produced no effect. As found by Malinowski, a strong field of 10,000 gauss merely increased the intensity of the radiation about 10 per cent. This added light was found to be unpolarized. (2) Sodium $D$ line. In the case of sodium vapor the tube was heated to 185\ifmmode^\circ\else\textdegree\fi{}C, the observations were visual, and as a source of unreversed light, the glow on the surface of a sodium glass vacuum tube carrying a discharge, was used. The effects observed are similar to those for mercury, but differ for some directions; fields forty times stronger were required, and the polarization in zero field was only 6 per cent, probably due to traces of hydrogen. This was increased by the field in some directions to 30 per cent.Effect of magnetic field on fluorescent light of iodine vapor and on white scattered light from mercury and ether vapors.---The polarization was found not to be affected.

DOI
10.1103/physrev.24.243

Related papers

On the influence of magnetic fields on the polarisation of resonance radiation

Robert Williams Wood, A. Ellett

Abstract The emission of polarised light by fluorescent sodium and iodine vapours was discovered by one of the present writers many years ago, and a similar phenomenon was looked for repeatedly, but without success, in the case of the much simpler (presumably) type of emission which occurs when a gas or vapour re-emits without change of wave-length the energy which it abstracts from the incident beam, as when the monochromatic radiation 2536 from a mercury arc traverse as exhausted quartz bulb containing a drop of mercury at room temperature, or the light of a sodium flame falls upon a glass bulb containing highly rarefied sodium vapour. Lord Rayleigh has recently discovered, however, that the resonance radiation of mercury vapour shows fairly strong polarisation, and reported results which apparently indicated that the polarisation becomes stronger as the exciting radiation penetrates to greater and greater depths of the vapour, being practically absent at the point where the radiation enters the bulb or tube. This would mean that polarisation of the light results only when the excitation is, by frequencies, a little out of tune with the natural frequency of the mercury atom, a matter of great theoretical interest. In a report of some work done last year by one of us this last observation of Lord Rayleigh was not confirmed, the polarisation appearing of full strength right up to the entrance window of the exciting beam. A possible explanation of Lord Rayleigh's results will be offered in the present paper in which it will be shown that a very weak magnetic field, properly oriented, destroys completely all traces of polarisation.

Proceedings of the Royal Society of London Series A Containing Papers of a Mathematical and Physical Character•Jun 1, 1923•48 citations

Polarization of Radiation Excited by Electron Impact

A. Ellett, Paul D. Foote, Fred L. Mohler

Polarized radiation following electron impact.---If a unidirectional beam of electrons, of velocity slightly in excess of the resonance potential, is projected through a vapor at a very low pressure so that effects due to atomic collision and resonance radiation are negligible, and in the absence of an applied field and resulting Larmor precession, there is reason to suspect that the radiation emitted perpendicular to the electron beam should be partially polarized, especially for lines corresponding to $\ensuremath{\Delta}j=1$.Polarization in mercury and sodium vapor.---Experiment showed a polarization of about 30 percent for $\ensuremath{\lambda}2537$ with the greatest intensity of the electrical vibration having a direction perpendicular to the electron beam. No polarization was detected for the unresolved sodium D-lines, confirming the recent observation of Kossel and Gerthsen.Polarization in mercury with field of 3 gauss.---A field parallel to the electron beam produced no effect. With the field perpendicular to the beam the radiation along the field was unpolarized while that perpendicular to the field was reduced in polarization to 13 percent. These results suggest that the atom radiates with the same distribution of polarization and intensity as in zero field but with the atom rotated through an angle determined by the time of excitation and the precessional velocity.

Physical Review•Jan 1, 1926•19 citations

Effect of a Magnetic Field Upon the Polarization of Impact Radiation

W.H. McCorkle

Sodium $D$ line radiation excited by electrons moving parallel to a magnetic field of 300 gauss or more shows about 16 percent polarization, the major electric vibration being parallel to the direction of the exciting electron beam. In fields below 300 gauss the polarization is less, decreasing to zero in the absence of a field. That the polarization changes in a magnetic field must be due to the fact that the $3^{2}P_{\frac{3}{2}}$ level is a hyperfine multiplet which undergoes a Paschen-Back effect.

Physical Review•Sep 15, 1935•0 citations

Fluorescent emission of the mercury line 2537 A at pressures between 10-3 and 10-1 mm

Peter Pringsheim, Olive D. Saltmarsh

Abstract In his first papers on the resonance radiation of mercury and sodium Wood describes how the character of the emission changes with increasing pressure of the fluorescent vapour. At low pressure (p = 10-3 mm) the emission comes wholly from a narrow well-defined beam corresponding to the path of the primary light (beam fluorescence). With increasing density of the vapour the beam becomes diffuse until the luminosity fills the whole volume (volume fluorescence) and finally at pressures of about 0·1 mm it withdraws entirely to the spot of entrance of the primary light (surface fluorescence). In all three cases the absorption and emission of light are due to normal atoms; the phenomenon is that of normal or true resonance radiation. For the D-lines of sodium, Lord Rayleigh showed as early as 1919 that, even at pressures at which the true resonance radiation is concentrated on the surface, an emission can in addition be observed within the volume along the path of the primary light, if the D-lines in the spectrum of the exciting source are not too narrow. This new fluorescence beam which can only be excited by the outer parts of the D-lines is partially polarized. Later Jablonsky and Pringsheim found that though the normal resonance radiation observed on the surface is unpolarized under these conditions, the degree of polarization of the new fluorescence beam can be as high as 30% and is practically unaltered by the action of a magnetic field. For the mercury resonance line 2537 A it was Rayleigh who again studied the phenomena at higher pressures but with his main interest concentrated on the duration of the processes and on the appearance of the well-known mercury bands. In his paper, the continuous change of the fluorescence in the vapour volume is studied from room temperature up to 200°C. He used as a source of excitation a “not fully cooled” mercury lamp, giving a somewhat broadened and partially self-reversed line at 2537 A, which produces the effect called by Rayleigh “core­ effect”. The latter is in Rayleigh’s terminology the fluorescence of mercury vapour produced by the more central part of the 2537 A line while the very different fluorescence emission which is excited by a much broadened and self-reversed line is called by him the wing effect. The core effect always shows a line which, with the available dispersion, seems to coincide with the resonance line itself; when the pressure increases, a number of bands appear which have no importance for the present paper. Since in saturated vapour at 100° C the normal resonance radiation has withdrawn to the surface, it is improbable that the core effect is produced by the most central region of the primary line by which the normal resonance radiation at the lowest pressures is excited.

Proceedings of the Royal Society of London A Mathematical and Physical Sciences•Mar 2, 1936•0 citations

Secondary Radiation and Polarization of Resonance Radiation in Cadmium

Walter A. MacNair

Secondary radiation in cadmium vapor containing mercury as an impurity.---Attention is called to the points of difference between the conditions under which the two types of optically excited spectra of mercury vapor appear, namely resonance radiation and fluorescence. In the present experiments it is noted that when a bulb containing cadmium with a slight impurity of mercury is illuminated by light of 2288A wave-length the secondary radiation contains the mercury line 2536.7A in addition to the cadmium lines 2288A and 3261A provided the metal is distilling. As soon as the vapor is stagnant, however, only the cadmium 2288A line appears. The suggestion is made that the phenomenon is due to the presence in the distilling vapor of unstable HgCd molecules. In such a molecule the Cd atom may absorb the 2288A radiation and subsequently in the breakdown of the molecule may excite the Hg atom by a collision of the second kind.Polarization of the cadmium resonance, radiation in zero magnetic field.---The polarization of the cadmium resonance radiation (3261A) in zero magnetic field under certain conditions was found to be 35 percent. In order to explain this value by the kinetic theory, one must assign effective radii to the colliding atoms which are thirty times the radii effective in ordinary collisions.

Physical Review•May 1, 1927•5 citations

Polarization of Resonance Radiation in Mercury

Harry F. Olson

$1^{1}S_{0}\ensuremath{-}2^{3}P_{1}$ of mercury excited by plane polarized light shows incomplete polarization both in the absence and in the presence of a weak field parallel to the electric vector. The amount of initial polarization depends upon the relative intensities of the hyperfine structure lines in the exciting light. The polarization with various relative orientations of field and light vector and the variation of polarization with field intensity in weak fields may be interpreted successfully by means of a semi-classical model, with proper relative intensities parallel and prependicular to the light vector, rotating after excitation with an angular velocity $\frac{\mathrm{geH}}{2mc}$ and emitting a damped wave. From curves connecting depolarization, rotation of maximum of polarization, etc., with field intensity $\ensuremath{\alpha}$, the damping constant, has been found to be 1.02 (\ifmmode\pm\else\textpm\fi{}0.02) ${10}^{7}$ ${\mathrm{sec}}^{\ensuremath{-}1}$.

Physical Review•Sep 1, 1928•14 citations
Effect of a magnetic field on the polarization of resonance radiation of mercury and of sodium.---(1) Mercury \ensuremathλ2536\ensuremath{\lambda}2536\ensuremathλ2536. A beam of plane polarized monochromatic light was focussed on the bulb containing the vapor at low pressure (0\ifmmode^\circ\else\textdegree\fi{}C), and the polarization of the resonance radiation was determined photographically with the aid of a quartz wedge and a double image quartz prism. If the exciting beam is going east with the electric vector vertical, when the earth's field is carefully neutralized the polarization is 90 per cent in any horizontal direction and zero vertically; a field of only 2 gauss directed north reduces the polarization in its direction to nearly zero (the decrease with increasing field being exponential), changes the polarization east and also up to 60 percent, and increases the intensity directed upwards threefold. Similar effects are produced by fields in other directions. The polarization with zero field does not approach 100 per cent at low pressures, since 90 per cent was found also with the vapor at -50\ifmmode^\circ\else\textdegree\fi{}C, when the radiation first appeared. It was thought that the high value might be due to an orientation of the resonating atom by the field of the exciting light, but a beam of concentrated sunlight produced no effect. As found by Malinowski, a strong field of 10,000 gauss merely increased the intensity of the radiation about 10 per cent. This added light was found to be unpolarized. (2) Sodium DDD line. In the case of sodium vapor the tube was heated to 185\ifmmode^\circ\else\textdegree\fi{}C, the observations were visual, and as a source of unreversed light, the glow on the surface of a sodium glass vacuum tube carrying a discharge, was used. The effects observed are similar to those for mercury, but differ for some directions; fields forty times stronger were required, and the polarization in zero field was only 6 per cent, probably due to traces of hydrogen. This was increased by the field in some directions to 30 per cent.Effect of magnetic field on fluorescent light of iodine vapor and on white scattered light from mercury and ether vapors.---The polarization was found not to be affected.
Abstract The emission of polarised light by fluorescent sodium and iodine vapours was discovered by one of the present writers many years ago, and a similar phenomenon was looked for repeatedly, but without success, in the case of the much simpler (presumably) type of emission which occurs when a gas or vapour re-emits without change of wave-length the energy which it abstracts from the incident beam, as when the monochromatic radiation 2536 from a mercury arc traverse as exhausted quartz bulb containing a drop of mercury at room temperature, or the light of a sodium flame falls upon a glass bulb containing highly rarefied sodium vapour. Lord Rayleigh has recently discovered, however, that the resonance radiation of mercury vapour shows fairly strong polarisation, and reported results which apparently indicated that the polarisation becomes stronger as the exciting radiation penetrates to greater and greater depths of the vapour, being practically absent at the point where the radiation enters the bulb or tube. This would mean that polarisation of the light results only when the excitation is, by frequencies, a little out of tune with the natural frequency of the mercury atom, a matter of great theoretical interest. In a report of some work done last year by one of us this last observation of Lord Rayleigh was not confirmed, the polarisation appearing of full strength right up to the entrance window of the exciting beam. A possible explanation of Lord Rayleigh's results will be offered in the present paper in which it will be shown that a very weak magnetic field, properly oriented, destroys completely all traces of polarisation.
Polarized radiation following electron impact.---If a unidirectional beam of electrons, of velocity slightly in excess of the resonance potential, is projected through a vapor at a very low pressure so that effects due to atomic collision and resonance radiation are negligible, and in the absence of an applied field and resulting Larmor precession, there is reason to suspect that the radiation emitted perpendicular to the electron beam should be partially polarized, especially for lines corresponding to $\ensuremath{\Delta}j=1$.Polarization in mercury and sodium vapor.---Experiment showed a polarization of about 30 percent for $\ensuremath{\lambda}2537$ with the greatest intensity of the electrical vibration having a direction perpendicular to the electron beam. No polarization was detected for the unresolved sodium D-lines, confirming the recent observation of Kossel and Gerthsen.Polarization in mercury with field of 3 gauss.---A field parallel to the electron beam produced no effect. With the field perpendicular to the beam the radiation along the field was unpolarized while that perpendicular to the field was reduced in polarization to 13 percent. These results suggest that the atom radiates with the same distribution of polarization and intensity as in zero field but with the atom rotated through an angle determined by the time of excitation and the precessional velocity.
Sodium DDD line radiation excited by electrons moving parallel to a magnetic field of 300 gauss or more shows about 16 percent polarization, the major electric vibration being parallel to the direction of the exciting electron beam. In fields below 300 gauss the polarization is less, decreasing to zero in the absence of a field. That the polarization changes in a magnetic field must be due to the fact that the 32P323^{2}P_{\frac{3}{2}}32P23​​ level is a hyperfine multiplet which undergoes a Paschen-Back effect.
Abstract In his first papers on the resonance radiation of mercury and sodium Wood describes how the character of the emission changes with increasing pressure of the fluorescent vapour. At low pressure (p = 10-3 mm) the emission comes wholly from a narrow well-defined beam corresponding to the path of the primary light (beam fluorescence). With increasing density of the vapour the beam becomes diffuse until the luminosity fills the whole volume (volume fluorescence) and finally at pressures of about 0·1 mm it withdraws entirely to the spot of entrance of the primary light (surface fluorescence). In all three cases the absorption and emission of light are due to normal atoms; the phenomenon is that of normal or true resonance radiation. For the D-lines of sodium, Lord Rayleigh showed as early as 1919 that, even at pressures at which the true resonance radiation is concentrated on the surface, an emission can in addition be observed within the volume along the path of the primary light, if the D-lines in the spectrum of the exciting source are not too narrow. This new fluorescence beam which can only be excited by the outer parts of the D-lines is partially polarized. Later Jablonsky and Pringsheim found that though the normal resonance radiation observed on the surface is unpolarized under these conditions, the degree of polarization of the new fluorescence beam can be as high as 30% and is practically unaltered by the action of a magnetic field. For the mercury resonance line 2537 A it was Rayleigh who again studied the phenomena at higher pressures but with his main interest concentrated on the duration of the processes and on the appearance of the well-known mercury bands. In his paper, the continuous change of the fluorescence in the vapour volume is studied from room temperature up to 200°C. He used as a source of excitation a “not fully cooled” mercury lamp, giving a somewhat broadened and partially self-reversed line at 2537 A, which produces the effect called by Rayleigh “core­ effect”. The latter is in Rayleigh’s terminology the fluorescence of mercury vapour produced by the more central part of the 2537 A line while the very different fluorescence emission which is excited by a much broadened and self-reversed line is called by him the wing effect. The core effect always shows a line which, with the available dispersion, seems to coincide with the resonance line itself; when the pressure increases, a number of bands appear which have no importance for the present paper. Since in saturated vapour at 100° C the normal resonance radiation has withdrawn to the surface, it is improbable that the core effect is produced by the most central region of the primary line by which the normal resonance radiation at the lowest pressures is excited.
Secondary radiation in cadmium vapor containing mercury as an impurity.---Attention is called to the points of difference between the conditions under which the two types of optically excited spectra of mercury vapor appear, namely resonance radiation and fluorescence. In the present experiments it is noted that when a bulb containing cadmium with a slight impurity of mercury is illuminated by light of 2288A wave-length the secondary radiation contains the mercury line 2536.7A in addition to the cadmium lines 2288A and 3261A provided the metal is distilling. As soon as the vapor is stagnant, however, only the cadmium 2288A line appears. The suggestion is made that the phenomenon is due to the presence in the distilling vapor of unstable HgCd molecules. In such a molecule the Cd atom may absorb the 2288A radiation and subsequently in the breakdown of the molecule may excite the Hg atom by a collision of the second kind.Polarization of the cadmium resonance, radiation in zero magnetic field.---The polarization of the cadmium resonance radiation (3261A) in zero magnetic field under certain conditions was found to be 35 percent. In order to explain this value by the kinetic theory, one must assign effective radii to the colliding atoms which are thirty times the radii effective in ordinary collisions.
$1^{1}S_{0}\ensuremath{-}2^{3}P_{1}$ of mercury excited by plane polarized light shows incomplete polarization both in the absence and in the presence of a weak field parallel to the electric vector. The amount of initial polarization depends upon the relative intensities of the hyperfine structure lines in the exciting light. The polarization with various relative orientations of field and light vector and the variation of polarization with field intensity in weak fields may be interpreted successfully by means of a semi-classical model, with proper relative intensities parallel and prependicular to the light vector, rotating after excitation with an angular velocity geH2mc\frac{\mathrm{geH}}{2mc}2mcgeH​ and emitting a damped wave. From curves connecting depolarization, rotation of maximum of polarization, etc., with field intensity $\ensuremath{\alpha}$, the damping constant, has been found to be 1.02 (\ifmmode\pm\else\textpm\fi{}0.02) 107{10}^{7}107 ${\mathrm{sec}}^{\ensuremath{-}1}$.