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Physical Review Letters

Polarization of S122 Ground State of Even Isotopes of Hg+ by Stepwise Electron Impact

C. H. Liu, Richard Lien-Chao King, H. Henry Stroke

Published Aug 4, 1969• 6 citations
Publisher

Abstract

The $6s^{2}S_{\frac{1}{2}}$ ground ionic state of even isotopes of mercury was polarized in a stepwise excitation process from the atomic $6{s}^{2}^{1}S_{0}$ ground state via the metastable $6s6p^{3}P_{2}$ state. The latter was optically pumped with polarized 5461-\AA{} ($6s7s^{3}S_{1}\ensuremath{-}^{3}P_{2}$) radiation. Paramagnetic resonance, observed by monitoring the change in intensity of the relatively intense 2851-\AA{} ($5{d}^{9}6{s}^{2}^{2}D_{\frac{5}{2}}\ensuremath{-}5{d}^{10}6s^{2}S_{\frac{1}{2}}$) electric quadrupole resonance radiation, was used to determine the polarization of the even-isotope ground-state ion to be 15%. If one assumes conservation of spin angular momentum, this process should yield highly polarized electrons.

DOI
10.1103/physrevlett.23.209

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Experimental Evidence of the Inversion of Angular Momentum During the Transfer of Excitation by Resonant Collisions in the 6P13 State of Mercury

B. Dodsworth, A. Omont

The zero-field level-crossing signal of even isotopes of natural Hg excited by resonant collisions from directly excited ${\mathrm{Hg}}^{198}$ atoms has been observed with circularly polarized light. The signal is proportional to the atomic "orientation" (mean value of the angular momentum of the excited atoms). The sense of this orientation is reversed when the excitation is transferred by collisions from ${\mathrm{Hg}}^{198}$ to other isotopes, as predicted by the theory.

Physical Review Letters•Feb 2, 1970•9 citations

A New "Double Resonance" Method for Investigating Atomic Energy Levels. Application to Hg P 1 3

J. Brossel, Francis Bitter

Excitation of atoms in a vapor by polarized light produces unequal population of the magnetic sublevels of the excited state. The emitted optical resonance radiation is therefore partly polarized. The application of radiofrequency or microwave fields at a magnetic resonance frequency will induce transitions between sublevels of the excited state. The degree of polarization of the emitted optical resonance radiation is altered when the magnetic resonance condition is fulfilled. As suggested by Brossel and Kastler, this effect may be used to reveal the structure of the energy level. A detailed theory applicable to, and experiments on the $^{3}P_{1}$ state of all the isotopes of mercury are reported. The results obtained indicate that double resonance phenomena constitute a valuable new tool for investigating the structure of atomic energy levels. The mean life of the $^{3}P_{1}$ state is shown by observations on the resonance line widths to be 1.55\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}7}$ sec for all the isotopes. The $g$-factor of the $^{3}P_{1}$ state for isotopes with zero spin, measured in terms of the proton $g$-factor, is 1.4838\ifmmode\pm\else\textpm\fi{}0.0004.

Physical Review•May 1, 1952•373 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

Radio-Frequency Resonance of the Metastable State (2P322 3S122)2 of Neon Produced and Aligned by Electron Impact

T. Hadeishi, Orilla A. McHarris, William A. Nierenberg

The metastable state ${(2^{2}P_{\frac{3}{2}} 3^{2}S_{\frac{1}{2}})}_{2}$ of neon was produced and aligned by electron impact. The diodestructure electron gun was operated at a high electron-current density under space-charge neutralization conditions. Radio-frequency resonance of the aligned metastable state ${(2^{2}P_{\frac{3}{2}} 3^{2}S_{\frac{1}{2}})}_{2}$ was observed by monitoring the change of absorption of the $\ensuremath{\lambda}6143$-resonance radiation passing through the gap between the cathode and anode. The neon metastable-state resonance was compared with the mercury metastable-state $6^{3}P_{2}$ radio-frequency resonance obtained by using the same gun for both, and observed by monitoring the absorption of the $\ensuremath{\lambda}5461$-resonance radiation passing through the same excitation region. The observed $\frac{{({g}_{J})}_{\mathrm{Ne}}}{{({g}_{J})}_{\mathrm{Hg}}}$ was 1.008\ifmmode\pm\else\textpm\fi{}0.024. This method could be applied to other atoms having a metastable state with $J>0$.

Physical Review•May 17, 1965•9 citations

Hyperfine Structure and the Polarization of Resonance Radiation. II. Magnetic Depolarization and the Determination of Mean Lives

Allan C. G. Mitchell

Breit has derived formulae giving the polarization $P(H)$ and the angle of maximum polarization $\ensuremath{\theta}$ of a resonance line showing hyperfine structure, as a function of a weak magnetic field applied in the direction of observation of the resonance radiation. The formulae give a means of estimating the effect of hyperfine structure on the calculation of the mean life $\ensuremath{\tau}$ of an excited atom from experiments on the magnetic depolarization and rotation of the plane of polarization of resonance radiation. The calculation has been carried through for the case of the resonance line of $\mathrm{Cd}(\ensuremath{\lambda}3261)$ and that of $\mathrm{Hg}(\ensuremath{\lambda}2537)$, and it is found that the differences between the value of $\ensuremath{\tau}$ calculated from hyperfine structure data and that calculated from $tan2\ensuremath{\theta}$ by the usual non-hyperfine structure method lie well within the experimental error. $\frac{P(H)}{{P}_{0}}$ is found to be practically the same whether hyperfine structure is taken into account or neglected. This is due to the fact that the greatest contribution of the polarization in these cases comes from the isotopes having no nuclear spin and the $g$-value for the upper state of these isotopes is larger than any other upper hyperfine structure state involved. The mean lives of the $7^{3}S_{1}$ state of mercury have been recalculated from Richter's data on the polarization of stepwise radiation. The values of $\ensuremath{\tau}$ obtained by this method of calculation are 7.2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}9}$ for $\ensuremath{\lambda}4047$, 1.69\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ for $\ensuremath{\lambda}4358$ and 1.53\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ for $\ensuremath{\lambda}5461$. A discussion of Richter's results is given.

Physical Review•Jun 1, 1933•1 citation

A stepwise electron-photon coincidence experiment on the 61P1 state of mercury

Andrew James Murray

A new type of electron/photon coincidence experiment is presented which utilises a laser -electron stepwise excitation technique to prepare atoms in an excited state. An electron collision initially excites an atom from the ground state to an intermediate state. Following this electron excitation process, coherent single mode laser radiation further excites the atom to an upper state, from which the fluorescence is observed. The nature of the laser excitation transfers both amplitude and phase information about the electron excited state to the upper excited state in a coherent way. This information is extracted from the upper state fluorescence by analysis of the fluorescence polarization in coincidence with the electron scattered from the atom for particular polarizations of the laser radiation. The coincidence technique allows an identically prepared sub -ensemble of excited atoms to be selected for measurement. The electron excited state studied was the 61131 state of mercury, excited by a beam of unpolarized electrons at an impact energy of 16 eV. The mercury atomic beam was isotopically selected following electron excitation using the narrow bandwidth of the laser radiation. Excitation from the electron excited 61P1 state was via 579 nm laser radiation to the 61D2 state and fluorescence was monitored from this state to the 63P1 state via a 313 nm transition. Stokes parameters were measured for two different laser polarization angles, since this allowed a complete set of collision parameters to be deduced for a single experimental geometry. Results for three different scattering angles at this energy are presented. The laser excitation process was modelled in both the weak and the strong laser excitation regimes. A perturbation approach developed to model single photon laser excitation allowed the collision parameters to be extracted from the measured coincidence Stokes parameters analytically, whereas a Quantum Electrodynamic model allowed high laser intensity effects on the coincidence signal to be explored theoretically. The Quantum Electrodynamic model indicated that the weak excitation model could be used to extract the collision parameters from the Stokes parameters at the laser intensities used in the experiment. Effects due to variation of the laser intensity were predicted from the Quantum Electrodynamic model and experiments conducted to test these predictions are presented. Collision parameters deduced from the measured stepwise coincidence Stokes parameters following optimization of the experimental conditions are presented. These parameters are compared qualitatively with existing data from heavy atomic systems and with a theoretical model based upon the Distorted Wave Born Approximation. Similarities between the experimental data are found, however significant discrepancies are noted between the parameters obtained here and with the predictions of the theoretical model.

•Jan 1, 1989•0 citations
The 6s2S126s^{2}S_{\frac{1}{2}}6s2S21​​ ground ionic state of even isotopes of mercury was polarized in a stepwise excitation process from the atomic 6{s}^{2}^{1}S_{0} ground state via the metastable 6s6p3P26s6p^{3}P_{2}6s6p3P2​ state. The latter was optically pumped with polarized 5461-\AA{} (6s7s3S1\ensuremath−3P26s7s^{3}S_{1}\ensuremath{-}^{3}P_{2}6s7s3S1​\ensuremath−3P2​) radiation. Paramagnetic resonance, observed by monitoring the change in intensity of the relatively intense 2851-\AA{} (5{d}^{9}6{s}^{2}^{2}D_{\frac{5}{2}}\ensuremath{-}5{d}^{10}6s^{2}S_{\frac{1}{2}}) electric quadrupole resonance radiation, was used to determine the polarization of the even-isotope ground-state ion to be 15%. If one assumes conservation of spin angular momentum, this process should yield highly polarized electrons.
The zero-field level-crossing signal of even isotopes of natural Hg excited by resonant collisions from directly excited Hg198{\mathrm{Hg}}^{198}Hg198 atoms has been observed with circularly polarized light. The signal is proportional to the atomic "orientation" (mean value of the angular momentum of the excited atoms). The sense of this orientation is reversed when the excitation is transferred by collisions from Hg198{\mathrm{Hg}}^{198}Hg198 to other isotopes, as predicted by the theory.
Excitation of atoms in a vapor by polarized light produces unequal population of the magnetic sublevels of the excited state. The emitted optical resonance radiation is therefore partly polarized. The application of radiofrequency or microwave fields at a magnetic resonance frequency will induce transitions between sublevels of the excited state. The degree of polarization of the emitted optical resonance radiation is altered when the magnetic resonance condition is fulfilled. As suggested by Brossel and Kastler, this effect may be used to reveal the structure of the energy level. A detailed theory applicable to, and experiments on the 3P1^{3}P_{1}3P1​ state of all the isotopes of mercury are reported. The results obtained indicate that double resonance phenomena constitute a valuable new tool for investigating the structure of atomic energy levels. The mean life of the 3P1^{3}P_{1}3P1​ state is shown by observations on the resonance line widths to be 1.55\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}7}$ sec for all the isotopes. The ggg-factor of the 3P1^{3}P_{1}3P1​ state for isotopes with zero spin, measured in terms of the proton ggg-factor, is 1.4838\ifmmode\pm\else\textpm\fi{}0.0004.
$1^{1}S_{0}\ensuremath{-}2^{3}P_{1}$ 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 ${\mathrm{sec}}^{\ensuremath{-}1}$.
The metastable state (22P3232S12)2{(2^{2}P_{\frac{3}{2}} 3^{2}S_{\frac{1}{2}})}_{2}(22P23​​32S21​​)2​ of neon was produced and aligned by electron impact. The diodestructure electron gun was operated at a high electron-current density under space-charge neutralization conditions. Radio-frequency resonance of the aligned metastable state (22P3232S12)2{(2^{2}P_{\frac{3}{2}} 3^{2}S_{\frac{1}{2}})}_{2}(22P23​​32S21​​)2​ was observed by monitoring the change of absorption of the $\ensuremath{\lambda}6143$-resonance radiation passing through the gap between the cathode and anode. The neon metastable-state resonance was compared with the mercury metastable-state 63P26^{3}P_{2}63P2​ radio-frequency resonance obtained by using the same gun for both, and observed by monitoring the absorption of the $\ensuremath{\lambda}5461$-resonance radiation passing through the same excitation region. The observed (gJ)Ne(gJ)Hg\frac{{({g}_{J})}_{\mathrm{Ne}}}{{({g}_{J})}_{\mathrm{Hg}}}(gJ​)Hg​(gJ​)Ne​​ was 1.008\ifmmode\pm\else\textpm\fi{}0.024. This method could be applied to other atoms having a metastable state with J>0J>0J>0.
Breit has derived formulae giving the polarization P(H)P(H)P(H) and the angle of maximum polarization $\ensuremath{\theta}$ of a resonance line showing hyperfine structure, as a function of a weak magnetic field applied in the direction of observation of the resonance radiation. The formulae give a means of estimating the effect of hyperfine structure on the calculation of the mean life $\ensuremath{\tau}$ of an excited atom from experiments on the magnetic depolarization and rotation of the plane of polarization of resonance radiation. The calculation has been carried through for the case of the resonance line of $\mathrm{Cd}(\ensuremath{\lambda}3261)$ and that of $\mathrm{Hg}(\ensuremath{\lambda}2537)$, and it is found that the differences between the value of $\ensuremath{\tau}$ calculated from hyperfine structure data and that calculated from $tan2\ensuremath{\theta}$ by the usual non-hyperfine structure method lie well within the experimental error. P(H)P0\frac{P(H)}{{P}_{0}}P0​P(H)​ is found to be practically the same whether hyperfine structure is taken into account or neglected. This is due to the fact that the greatest contribution of the polarization in these cases comes from the isotopes having no nuclear spin and the ggg-value for the upper state of these isotopes is larger than any other upper hyperfine structure state involved. The mean lives of the 73S17^{3}S_{1}73S1​ state of mercury have been recalculated from Richter's data on the polarization of stepwise radiation. The values of $\ensuremath{\tau}$ obtained by this method of calculation are 7.2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}9}$ for $\ensuremath{\lambda}4047$, 1.69\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ for $\ensuremath{\lambda}4358$ and 1.53\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ for $\ensuremath{\lambda}5461$. A discussion of Richter's results is given.
A new type of electron/photon coincidence experiment is presented which utilises a laser -electron stepwise excitation technique to prepare atoms in an excited state. An electron collision initially excites an atom from the ground state to an intermediate state. Following this electron excitation process, coherent single mode laser radiation further excites the atom to an upper state, from which the fluorescence is observed. The nature of the laser excitation transfers both amplitude and phase information about the electron excited state to the upper excited state in a coherent way. This information is extracted from the upper state fluorescence by analysis of the fluorescence polarization in coincidence with the electron scattered from the atom for particular polarizations of the laser radiation. The coincidence technique allows an identically prepared sub -ensemble of excited atoms to be selected for measurement. The electron excited state studied was the 61131 state of mercury, excited by a beam of unpolarized electrons at an impact energy of 16 eV. The mercury atomic beam was isotopically selected following electron excitation using the narrow bandwidth of the laser radiation. Excitation from the electron excited 61P1 state was via 579 nm laser radiation to the 61D2 state and fluorescence was monitored from this state to the 63P1 state via a 313 nm transition. Stokes parameters were measured for two different laser polarization angles, since this allowed a complete set of collision parameters to be deduced for a single experimental geometry. Results for three different scattering angles at this energy are presented. The laser excitation process was modelled in both the weak and the strong laser excitation regimes. A perturbation approach developed to model single photon laser excitation allowed the collision parameters to be extracted from the measured coincidence Stokes parameters analytically, whereas a Quantum Electrodynamic model allowed high laser intensity effects on the coincidence signal to be explored theoretically. The Quantum Electrodynamic model indicated that the weak excitation model could be used to extract the collision parameters from the Stokes parameters at the laser intensities used in the experiment. Effects due to variation of the laser intensity were predicted from the Quantum Electrodynamic model and experiments conducted to test these predictions are presented. Collision parameters deduced from the measured stepwise coincidence Stokes parameters following optimization of the experimental conditions are presented. These parameters are compared qualitatively with existing data from heavy atomic systems and with a theoretical model based upon the Distorted Wave Born Approximation. Similarities between the experimental data are found, however significant discrepancies are noted between the parameters obtained here and with the predictions of the theoretical model.