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Showing papers on "Circular polarization published in 1974"



Journal ArticleDOI
TL;DR: In this paper, a theory of circular dichroism is developed through a direct calculation of the absorption rates for circularly polarized light on molecules, from this a differential rate as between left and right LPs is calculated.
Abstract: A theory of circular dichroism is developed through a direct calculation of the absorption rates for circularly polarized light on molecules. From this a differential rate as between left and right circularly polarized light is calculated. This is immediately related to the experimental data on circular dichroism. When the calculations are restricted to the dipole approximation we reproduce the rotatory strength in the form of a differential Einstein B coefficient. Higher moments are considered in detail and their effects analyzed for both the locked‐in situation and the case of randomly oriented molecular absorbers. A general expression is obtained for the differential absorption rate.

83 citations


Journal ArticleDOI
TL;DR: In this paper, a set of restrictions upon the magnetic field and visible angular size of a canonical nonthermal source (one whose emission is incoherent electron synchrotron) has been obtained.
Abstract: A set of restrictions upon the magnetic field and visible angular size of a canonical nonthermal source (one whose emission is incoherent electron synchrotron) has been obtained in another paper. The degree of electron anisotropy and magnetic field disordering were left as free parameters. In the present paper these restrictions are applied to the variable compact radio sources 3C 84, 3C 120, 3C 273, 3C 279, 3C 454.3, CTA 102, 3C 446, PKS 2134 + 004, VRO 42.22.01, and OJ 287. The theoretically derived angular sizes for these sources are in reasonable agreement with published VLBI sizes, provided that the characteristic pitch angles are not extremely small. The magnetic field strengths determined from the degree of circular polarization are generally compatible with field strengths derived from the self-absorption and synchrotron self-Compton conditions, again provided that the pitch angles are not too small. It is argued that the self-absorption optical depth cannot be much less than unity near the low-frequency turnovers; otherwise, serious discrepancies with observation result.

79 citations


Journal ArticleDOI
TL;DR: In this paper, a general discussion of the induction of optical activity by circularly polarized light is presented and three different mechanisms, or their combinations, can cause asymmetric induction, and particular attention is paid to the asymmetric synthesis of helicenes.
Abstract: The reactions induced by circularly polarized light are reviewed and a general discussion of the induction of optical activity by circularly polarized light is presented. It is concluded that three different mechanisms, or their combinations, can cause asymmetric induction. In each case the optical yield is dependent on the optical anisotropy factor g, the ratio between the circular dichroism (Δϵ) and the extinction coefficient (ϵ). The results are discussed in terms of the presumed mechanisms, and particular attention is paid to the asymmetric synthesis of helicenes. It is concluded that this kind of photochemistry may have analytical importance.

73 citations


Journal ArticleDOI
TL;DR: In this article, an expression for the intensity of electrons inelastically scattered from an atomic state prepared by optical pumping is derived for both linearly and circularly polarized light, and the expression is a sum of state multipoles, the coefficient of each multipole being a spherical harmonic in the polar coordinates of the light direction for circularly polarised light, or the direction of the electric vector for linearly polarized light times a weight function depending on the population of the initial state.
Abstract: An expression is derived for the intensity of electrons inelastically scattered from an atomic state prepared by optical pumping. The expression is a sum of state multipoles, the coefficient of each multipole being a spherical harmonic in the polar coordinates of the light direction for circularly polarized light, or the direction of the electric vector for linearly polarized light times a weight function depending on the population of the initial state. These weight functions are given in closed form for both linearly and circularly polarized light.

65 citations


Journal ArticleDOI
TL;DR: In this paper, the authors measured the acousto-optic figure of merit of a TeO2 crystal for the slowest shear sound wave propagation using circularly polarized incident light.
Abstract: The intensity of the diffracted light in an optically active crystal by anisotropic Bragg diffraction has been observed to depend strongly on the polarization condition of the incident light. The acousto‐optic figure of merit for this type of crystal, therefore, should be measured under careful selection of the polarization and geometrical condition of the incident light. The figure of merit Me(p2n6/ρv3) of a TeO2 crystal for the slowest shear sound wave propagation using circularly polarized incident light was found to be 1200 × 10−18 sec3/g at 6328 A rather than 793 × 10−18 sec3/g, as was previously reported by using arbitrarily polarized light. The previous measurement does not give a correct value of Me, according to the theory given above.

57 citations


Journal ArticleDOI
TL;DR: In this article, the optical orientation of free and bound excitons in CdS was investigated and the observed degrees of polarization are generally large and vary significantly with the exciting energy (a negative polarization is sometimes obtained).
Abstract: The optical orientation by circularly polarized light of free and bound excitons in CdS is reported and discussed. The observed degrees of polarization are generally large and vary significantly with the exciting energy (a "negative" polarization is sometimes obtained). These results, together with the effects of a magnetic field, provide a lot of information about the levels excited, the luminescent levels (lifetimes and disorientation times), and the transfer of polarization from the first to the second. The optical orientation by linearly polarized light is also observed for the first time in solids. It is shown why these unusual effects can be seen on free excitons and not on other levels. The additional information that they provide leads to a better comprehension of the mechanisms of thermalization of the excitons, and of the symmetry properties of $K\ensuremath{ e}0$ exciton states.

46 citations


Journal ArticleDOI
TL;DR: In this paper, a general theoretical method is developed for proper weighting in the process of summing of the contributions of the various photoselected molecules to the emitted light when Brownian rotational motion is frozen.
Abstract: The orientation of molecules excited by a beam of light is not isotropic as a rule. If rotatory Brownian motion is not fast during the lifetime of the excited state the polarization properties of the light emitted from the excited molecules will depend as a rule on the mode of photoselection of the molecules by the excitation beam. A general theoretical method is developed for proper weighting in the process of summing of the contributions of the various photoselected molecules to the emitted light when Brownian rotational motion is frozen. A formula is obtained for the calculation of the probabilities of emission of light of a specified polarization from the photoselected system. To use this formula average values of multiples of elements of the Euler matrix are to be evaluated first; the polarization properties of the emitted light are then obtained by insertion of the components of the electric and magnetic transition dipole moments characterizing the absorption and emission of light by the molecule under discussion. By use of this formula, the Perrin‐Jablonski formula for the linear polarization of emitted light is derived in a simple fashion. It is shown that for asymmetric molecules the degree of circular polarization of the emitted light is affected by photoselection if the electric transition moments responsible for absorption and emission are not parallel. It is of much interest that under such circumstances the angle between the emitting electric and magnetic dipole moments can in principle be obtained.

31 citations


Journal ArticleDOI
TL;DR: It is suggested that the intense circular dichroism of chloroplasts reflects specific chlorophyll-chlorophyll interactions in the light-harvesting pigment.
Abstract: Chloroplasts isolated from pea leaves display an intense circular dichroism in the range 600 to 720nm. Circularly polarized light is also differentially scattered by chloroplasts, and this effect can be confused with circular dichroism. By using an instrumental modification it was possible to distinguish, and record separately, the ellipticities of the transmitted light (circular dichroism) and of the scattered light in the same c.d. instrument. By means of a light-scattering apparatus, the intensity of unpolarized light scattered by chloroplasts was measured as a function of wavelength and of angle. This measurement allowed the aforementioned ellipticities to be corrected for mutual interference. At a concentration of 4mug of chlorophyll/ml (the optimum practical concentration of chloroplasts at which there was no significant interaction of scattering and absorption effects) spectra of true circular dichroism (circular differential absorption) and circular differential scattering were obtained. The former showed maxima, positive at 688nm and negative at 676nm, with an intensity Deltatheta=8.3m degrees .litre.(mg of chlorophyll)(-1).cm(-1). The latter had a maximum at 683nm with an intensity of +47m degrees with respect to the solvent baseline; this value is independent of the concentration of chloroplasts in dilute suspensions. It is suggested that the intense circular dichroism of chloroplasts reflects specific chlorophyll-chlorophyll interactions in the light-harvesting pigment. The advantages of this method for determining the c.d. of scattering suspensions over those of other investigators are discussed.

27 citations


Journal ArticleDOI
TL;DR: In this paper, the authors reported the ionization of atomic potassium by simultaneous absorption of three dye laser quanta, tuned through the two-photon resonances with the 6S1/2 and 4D3/2,5/2 states, and investigated the dependence of ionization probability on the laser wavelength for linearly and circularly polarized light.
Abstract: We report observations of the ionization of atomic potassium by simultaneous absorption of three dye laser quanta. The laser wavelength is tuned through the two‐photon resonances with the 6S1/2 and 4D3/2,5/2 states, and the dependence of the ionization probability on the laser wavelength is investigated for linearly and circularly polarized light. Our results are in agreement with the selection rules and theoretical estimates of the ionization probability.

24 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of electromagnetic waves of circular polarization incident on a magnetized plasma from ion waves propagating parallel to the external magnetic field is studied. And the relevance of the process to ionospheric modification experiments is discussed.
Abstract: Stimulated scattering of electromagnetic waves of circular polarization incident on a magnetized plasma from ion waves propagating parallel to the external magnetic field is studied. The relevance of the process to ionospheric modification experiments is discussed.


Journal ArticleDOI
TL;DR: The fluorescence spectra of several dansyl derivatives bound to anti-dansyl antibodics are shifted by about 60 nm to the blue, and the quantum yields are markedly enhanced, compared to their respective fluorescence properties in water.

Journal ArticleDOI
TL;DR: In this paper, the frequency shifts of a self-oscillating magnetometer with cesium vapor are studied quantitatively by solving rate equations for the atoms undergoing the action of a circularly polarized pumping light beam.
Abstract: The frequency shifts of a self‐oscillating magnetometer with cesium vapor are studied quantitatively by solving rate equations for cesium atoms undergoing the action of a circularly polarized pumping light beam. Particular attention is given to the frequency shifts due to the line asymmetry of the rf spectrum in the light transmitted through the vapor. The line asymmetry varies with the orientation of the light beam relative to the field to be measured, the intensity of the light, and the temperature of the absorption cell. As an effect of a buffer gas, two extreme cases are considered, i.e., the optically excited state is in the complete mixing state and in the nonmixing state. The results show the fact that the frequency shifts depend largely on the collisional mixing in the excited state and on the sense of the circular polarization of the light. In order to reduce the frequency shifts, a new type of magnetometer, called the symmetrized spectrum magnetometer, is discussed, in which two circularly polarized light beams with opposite sense are simultaneously applied to a partitioned absorption cell.

Journal ArticleDOI
TL;DR: In this article, the average and individual pulse polarization measurements at 430 MHz are presented for three pulsars: PSR 0823 + 26, PSR0834 + 06, and PSR 2303 + 30.
Abstract: Both average and individual pulse polarization measurements at 430 MHz are presented for three pulsars: PSR 0823 + 26, PSR 0834 + 06, and PSR 2303 + 30. In each case, the average Stokes parameter waveformes are found to depend on the individual pulse polarization properties in a complicated manner. The average waveforms are in general depolarized by pulse-to-pulse fluctuations in polarization state at a given longitude. Two of the three objects exhibit variations of both linear and circular polarization which are associated with quasi-periodic subpulse modulation phenomena in a manner similar to that reported for linear polarization in PSR 0809 + 74 by Taylor et al. (1971.).

Journal ArticleDOI
TL;DR: In this article, the feasibility of obtaining arbitrary polarization in both one and two-dimensional arrays of slots in dual mode bifurcated waveguides was demonstrated, where the radiating element consists of a pair of crossed slots in the sidewall of a rectangular waveguide that couple to even and odd waveguide modes.
Abstract: The feasibility of obtaining arbitrary polarization in both one- and two-dimensional arrays of slots in dual mode bifurcated Waveguides has been demonstrated. The radiating element consists of a pair of crossed slots in the sidewall of a bifurcated rectangular waveguide that couple to even and odd waveguide modes. One linear polarization is excited by the even or "sum" mode and the orthogonal linear polarization is excited by the odd or "difference" mode. By superposing the sum and difference modes in the proper amplitude and phase, any arbitrary polarization can be realized. A two-dimensional array consisting of eight waveguide linear arrays, ferrite phase shifters for scanning in the plane normal to the linear arrays, and a feed network for power distribution and polarization control was constructed. Good radiation performance for various polarizations was obtained. In the case of linear polarization, the cross polarization component was on the order of -25 dB and in the case of circular polarization, the axial ratio was on the order of 1 dB. The polarization was controlled with a ferrite phase shifter. Close-in sidelobes of better than 20 dB were obtained for all polarizations. The preceding performance characteristics were obtained over a scan range of \pm20\deg and over a 6 percent frequency band.

Journal Article
TL;DR: In this article, a general rule relating the polarity of broad-band (spectral range: 5250 A to 5350 A) circular polarization fields observed in sunspots to that of the corresponding magnetic fields was proposed.
Abstract: The present work proposes a general rule relating the polarity of broad-band (spectral range: 5250 A to 5350 A) circular polarization fields observed in sunspots to that of the corresponding magnetic fields. The rule is illustrated with observations of particular spots.

Journal ArticleDOI
TL;DR: In this article, the orientation of the plane of polarization as well as the degree of linear polarization of γ-radiation was investigated in an external magnetic field with respect to an external magnetometer.


Journal ArticleDOI
E. Schlomann1, J. Milne
TL;DR: In this article, the motion of domain walls induced by microwave pulses is described in high power phase shifters using ferrite toroids, and it is shown that a circularly polarized rf magnetic field of strength h o exerts substantially the same pressure on domain walls as a dc magnetic field applied along the domain axis.
Abstract: A new high power effect in ferrites, the motion of domain walls induced by microwave pulses is described. In high power phase shifters using ferrite toroids this effect can change the remanent magnetization and hence change the insertion phase of the device. A theoretical explanation of these effects is obtained by considering a partially magnetized ferrite material having uniaxial anisotropy and exposed to an rf magnetic field perpendicular to the anisotropy axis. Experiments at 3 GHz on a twin-slab (i.e., toroid) phase shifter at peak power levels up to 300 kW are in good agreement with the theoretical expectations. It is shown that a circularly polarized rf magnetic field of strength h o exerts substantially the same pressure on domain walls as a dc magnetic field applied along the domain axis and having the strength H_{z} = \gammah\min{o}\max{2}\omega w, where γ is the gyromagnetic ratio and ω the angular frequency. The rf generated pressure tends to shrink those domains in which the imposed sense of circular polarization coincides with the sense of the natural spin precession.


Journal ArticleDOI
TL;DR: In this article, a new method of calculating the radiative polarization of electrons in homogeneous magnetic fields, using the modified electron propagation function, was presented, which is based on a modified version of the electron polarization function.
Abstract: We present a new method of calculating the radiative polarization of electrons in homogeneous magnetic fields, using the modified electron propagation function.

Journal ArticleDOI
W. v. Drachenfels1, U. T. Koch1, R. D. Lepper1, Th.M. Müller1, W. Paul1 
TL;DR: In this article, a pulsed polarized electron source using the Fano effect on cesium is described in detail, and a frequency doubled dye laser producing 2 mJ/pulse at 305 nm is used as the source of circularly polarized light.
Abstract: A pulsed polarized electron source using the Fano effect on cesium is described in detail. A frequency doubled dye laser producing 2 mJ/pulse at 305 nm is used as the source of circularly polarized light. The light beam interacts with an array of 20 atomic beams. The atomic beam oven operates in a closed cycle thereby increasing running time by a factor of 30. Intensities of 3×109e−/0.5 μs with a polarization of 90% have been routinely obtained.



Journal ArticleDOI
TL;DR: In this article, a theory of a ring laser subject to a uniform, axial dc magnetic field is given in extension of the two-mirror standing-wave treatment by Sargent, Lamb, and Fork.
Abstract: A theory of a ring laser subject to a uniform, axial dc magnetic field is given in extension of the two-mirror standing-wave treatment by Sargent, Lamb, and Fork. The active medium consists of thermally moving atoms that have two electronic levels with arbitrary angular momenta. The electric field is treated classically for two circular polarizations of opposite sense in a cavity with any degree of cavity anisotropy. Losses due to backscattering are also included. In addition, the results of a generalized treatment are given which includes arbitrarily oriented magnetic field, a general state of electric field polarization, varying isotopic abundance, and hyperfine structure. The self-consistency requirement is used to obtain amplitude- and frequency-determining equations for multimode operation as functions of laser parameters. A general calculational technique, the "perturbation tree," is introduced in the calculation of the third-order component of the population matrix, greatly simplifying the algebra involved by allowing it to be abstracted in tabular form.

Journal ArticleDOI
TL;DR: A better stabilization of intensity and a well-defined rectilinear polarized beam are obtained by eliminating the polarizer and applying a magnetic field H of about 100 G perpendicular to the axis of the laser cavity, along 6 cm of the capillary tube of the Laser.
Abstract: A laser is described that gives successive longitudinal modes that are polarized in a rectilinear manner alternately, following two perpendicular directions $pi$ and sigma. If a fixed polarizer is placed on the outcoming beam, the passage of the modes within the Doppler line causes important fluctuations with time reaching 30 to 40 percent of the mean intensity. Rotation of the polarizer causes a modulation of the beam; the light intensity remains approximately stable within about 1 percent if the polarizer is placed at 45$sup 0$ to the $pi$ and sigma vibrations. A better stabilization of intensity and a well-defined rectilinear polarized beam are obtained by eliminating the polarizer and applying a magnetic field H of about 100 G perpendicular to the axis of the laser cavity, along 6 cm of the capillary tube of the laser. The beam becomes 99 percent polarized, and all the energy is emitted in the modes $pi$ parallel to the magnetic field H. (TFD)

Journal ArticleDOI
TL;DR: In this paper, the polarization state of the photoelectrons emitted by an assembly of ground state alkali atoms illuminated by circularly polarized light is described in terms of the Stokes vector formalism.
Abstract: The polarization state of the photoelectrons emitted by an assembly of ground state alkali atoms illuminated by circularly polarized light is described in terms of the Stokes vector formalism. The results indicate that there are several different experimental approaches available for testing theoretical predictions but they yield the same information about the underlying processes.

Journal ArticleDOI
TL;DR: In this paper, the Dirac equation for a particle with spin 1/2 and an anomalous magnetic moment in an external wave field is reduced to a set of coupled ordinary differential equations for a spin factor, in which the wave function differs from the corresponding one for a 'normal' particle.
Abstract: The Dirac equation for a particle with spin 1/2 and an anomalous magnetic moment in an external wave field is reduced to a set of coupled ordinary differential equations for a spin factor, in which the wavefunction differs from the corresponding one for a 'normal' particle. Exact solutions are given for a linearly polarized laser wave of finite length and for an infinitely extended plane wave with circular polarization.

Journal ArticleDOI
TL;DR: In this paper, a formalism was developed which expressed the polarization and asymmetry in terms of the half-off-shell transition matrix, and calculations were performed for several models of the weak parity-nonconserving N-N interaction.
Abstract: The circular polarization and asymmetry, about the incident neutron spin direction, of the photon released in the reaction n + p -+ d + y at thermal neutron energies are consequences of parity violation in the n-p interaction. A formalism is developed which expresses the polarization and asymmetry in terms of the half-off-shell transition matrix, and calculations are performed for several models of the weak parity-nonconserving N-N interaction. The results indicate that the polarization is sensitive to the choice of both the strong N-N interaction and weak N-N interaction while the asymmetry is sensitive mainly to the latter. The observed polarization is of the same sign and rather larger than that calculated with the conventional weak N-N potential. Difficulties in the present method indicate that this discrepancy cannot be regarded as significant.