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Showing papers on "Circular polarization published in 1978"


Journal ArticleDOI
TL;DR: In this article, a snapshot of circularly polarized light is depicted in Figure 1 where we see that the magnitude of the electric vector is constant to within a sign, while the direction of electric field vector is modulated.
Abstract: Circular dichroism (CD) is a special kind of electronic absorption spectroscopy that uses circularly polarized light rather than isotropic light. CD is a particularly useful technique because it is sensitive to the conformation of a molecule, and because it can be applied to randomly oriented molecules in solution and in the gas phase. For a molecule to exhibit a CD spectrum it must be asymmetric, that is, it must contain no plane or center of symmetry. Since most biological molecules are asymmetric, CD spectroscopy has been used extensively to investigate their conformation. It has also been used to investigate the electronic properties of chromophores when simple asymmetric derivatives of known conformation are available. Most readers will be familiar with plane-polarized light. With this type of polarization the direction of the electric field vector is constant to within a sign, while the magnitude of the electric vector is modulated. Circularly polarized light is the antithesis of plane-polarized light. A snapshot of circularly polarized light is depicted in Figure 1 where we see that the magnitude of the electric vector is

78 citations



Journal ArticleDOI
TL;DR: In this paper, the current distribution in a Tokamak was measured from the change of polarization of an electromagnetic wave traversing the plasma, and a simple numerical method was given for calculating the resulting polarization and illustrated by examples.
Abstract: Presents a theoretical development of a proposal for measuring the current distribution in a Tokamak from the change of polarization of an electromagnetic wave traversing the plasma. A simple numerical method is given for calculating the resulting polarization and is illustrated by examples. The effect of the radial variation of toroidal field is discussed. The analytic solution in the form of a series is used to obtain some properties of the output polarization.

61 citations


Journal ArticleDOI
TL;DR: A method by which the frequency shift equals 4N times the rotation rate, where N is the number of rotating components available, and a higher heterodyne frequency is possible than with the previously described techniques is described.
Abstract: Twyman-Green. This Letter describes a method by which the frequency shift equals 4N times the rotation rate, where N is the number of rotating components available. The advantage of this method over previously described methods is that a higher heterodyne frequency is possible than with the previously described techniques. Let the light entering an interferometer, shown in Fig. 1, be separated into two orthogonal linear polarizations using, for example, a polarization beam splitter P. Each component travels a separate path through the interferometer cavity seeing a different optical phase retardation. Upon recombination the light passes through the frequency shifter and onto a detector plane, where the temporally varying optical signal has a phase equal to the net phase difference between the two paths inside the interferometer. The frequency shifter, which we shall describe using Jones calculus 3 and the complex wave representation of light, consists of a stationary quarterwave plate (QS) followed by a series of rotating halfwave plates (Hr) separated by stationary halfwave plates (HS), followed by a stationary linear polarizer (LS). The following analysis demonstrates a frequency shift of eight times the rotation rate of the halfwave plates. We begin by treating the horizontal (X) component, which we represent by

60 citations


Journal ArticleDOI
01 Jan 1978-Icarus
TL;DR: In this paper, multiple scattering calculations are performed in order to investigate the nature of the circular polarization of sunlight reflected by planetary atmospheres, and results are also computed for second-order scattering and for a simpler semiquantitative model of scattering by two particles.

53 citations



Journal ArticleDOI
TL;DR: A polarized electron source based upon the photoionization of unpolarized Cs atoms by circularly polarized light by Fano effect has been developed and applied to the study of spin dependence in low-energy electron-atom scattering.
Abstract: A polarized electron source based upon the photoionization of unpolarized Cs atoms by circularly polarized light (Fano effect) has been developed and applied to the study of spin dependence in low‐energy electron–atom scattering. Electron intensities of 10 nA with polarizations of 0.63±0.03 have been obtained routinely during continuous runs of up to 75 h. Frequent optical reversal of the direction of the longitudinal electron polarization minimizes systematic effects so that helicity dependent electron‐scattering asymmetries smaller than 4×10−4 can be measured.

34 citations


Patent
17 Jul 1978
TL;DR: In this paper, a microstrip antenna is disclosed having an etched metal radiator element including a polarizing patch consisting of a two dimensional removal of metallization from the central portion of the radiator element with one dimension of the polarization patch being greater than the other dimension.
Abstract: A microstrip antenna is disclosed having an etched metal radiator element including a polarizing patch consisting of a two dimensional removal of metallization from the central portion of the radiator element with one dimension of the polarization patch being greater than the other dimension e.g. an elongated rectangle and selectively oriented with respect to the input axis whereby, for example, circular polarization is achieved by means of orienting the polarization patch substantially 45° with respect to the input axis.

33 citations


Journal ArticleDOI
TL;DR: In this paper, measurements at 2.86 GHz of 57 spheroidal samples at all aspect angles in the low-resonance region are presented, and the results are readily convertible to linear (or any other) polarization.
Abstract: Measurements at 2.86 GHz of the backscatter matrix of 57 spheroidal samples at all aspect angles in the low-resonance region are presented. Sample size ranges up to ka = 3.4 , and axial ratios of 0.5, 0.6, and 0.8 have been used. Dielectric constants include 2.6, 3.3, and 6.5. The presentation is in terms of circular polarization, but the results are readily convertible to linear (or any other) polarization.

33 citations


Journal ArticleDOI
TL;DR: In this paper, the authors studied the very rapid variations in total flux density and circular polarization of HR 1099 at 2695 and 8085 MHz during the outburst of February 1978, and found that the radio emission is gyrosynchrotron radiation emitted by energetic electrons that are injected into an ordered magnetic field.
Abstract: We studied the very rapid variations in total flux density and circular polarization of HR 1099 at 2695 and 8085 MHz during the outburst of February 1978. From these observations we find the following. (1) The flux density and the activity (percent variation) at 8085 MHz are greater than at 2695 MHz: the radio spectrum has a positive slope, Sproportional..nu../sup ..cap alpha../ with ..cap alpha..>0. (2) Often the radio emission is circularly polarized at both frequencies, although the polarity may be different at the two frequencies. (3) The degree of circular polarization is generally greater at 2695 MHz than it is at 8085 MHz; we find the degree of polarization at 2695 MHz to be as high as approx.40%. (4) During active periods of several hours duration we see changes approx. factor of 2 in flux density at 2695 MHz that are wholly confined to one sense of circular polarization: the activity is altogether absent in the opposite polarity. (5) During two distinct epochs when the circular polarization at 2695 MHz was large, we find evidence for a characteristic sinusoidal modulation of the left circular flux density with a period of approx.4 min; this modulation appears to recur at intervalsmore » of 4.5--5.5 min. (6) Large degrees of circular polarization (> or approx. =10%) occur only when the phase of the HR 1099 binary system is near zero, that is, at conjunction with the more active component in front. These data support the conclusion that the radio emission is gyrosynchrotron radiation emitted by energetic electrons that are injected into an ordered magnetic field. The correlation of the degree of circular polarization with orbital phase when the source is active suggests that the magnetic field is a property of the binary system: it is shared by two stars.« less

30 citations


Journal ArticleDOI
R.D. Wengenroth1
TL;DR: In this article, phase and polarization shifting techniques at a reflecting surface cause the illumination to be transduced to form a pencil beam, instead of a conical one, for long waveguide runs at power levels above those readily handled by standard waveguide.
Abstract: At power levels above those readily handled by standard waveguide, and for long waveguide runs, the TE/sub 01/ mode in circular guide is a preferred transmission line approach. At the antenna, this mode is generally unsuited to radiation since it forms a conical, instead of a pencil beam. Phase and polarization shifting techniques at a reflecting surface cause the illumination to be transduced to form a pencil beam. The techniques have been demonstrated in a 33-GHz model.


Journal ArticleDOI
TL;DR: In this article, the authors studied quantitatively the circular polarization of rotationally resolved features in the laser-induced fluorescence from I2 excited by the 5145 A argon laser line and its variation with various experimental parameters such as light intensity, iodine and foreign gas pressure.
Abstract: We have studied quantitatively the circular polarization of rotationally resolved features in the laser-induced fluorescence from I2 excited by the 5145 A argon laser line, and its variation with various experimental parameters such as light intensity, iodine and foreign gas pressure. Optical pumping of the ν″ = 0, J″ = 13 level of 1Σ g + has been unambiguously demonstrated and the variation of C with gas pressure has been analysed to yield cross sections for elastic and inelastic collisions which relax the oriented ground state. Experiments on the dipolar array of oriented 3Π0u + molecules at very high pressures show that the circular polarization ratio does not change under conditions of many gas kinetic collisions per lifetime. This indicates that a selection rule ΔM = 0 operates on elastic collisions of I2* with other atoms and molecules, which appears to be rigorously adhered to.


Journal ArticleDOI
TL;DR: In this article, the dynamics of multilevel excitation by coherent radiation, in the N-level rotating-wave approximation, when the levels have nonzero angular momentum J and consequent spatial-orientation degeneracy 2J + 1.
Abstract: This paper describes the dynamics of multilevel excitation by coherent radiation, in the N-level rotating-wave approximation, when the levels have nonzero angular momentum J and consequent spatial-orientation degeneracy 2J + 1. Observable populations average over 2J + 1 independent sublevel excitation sequences. The phenomenon of inaccessible sublevels is noted, as is the effect of polarization. The paper illustrates how averaging over orientation can, in some cases, render illegible the Rabi oscillations and the ac Stark effect, whereas in other cases (J ..-->.. J, circular polarization on J ..-->.. J +- 1 linear polarization) appreciable structure remains.

Book ChapterDOI
TL;DR: In this paper, the occurrence of circularly polarized light in the luminescence of chiral molecules can be rationalized in terms of the known correspondence between absorption and emission processes.
Abstract: Publisher Summary This chapter focuses on circularly polarized luminescence. It investigates specifically how it is measured and what it may reveal about the molecules producing it. The occurrence of circularly polarized light in the luminescence of chiral molecules can be rationalized in terms of the known correspondence between absorption and emission processes. For a transition between two defined quantum levels, the probability of spontaneous emission is proportional to the probability of absorption at unit light intensity, and this is expected to hold separately for right-handed and left-handed circularly polarized light. In addition, there is another feature in circularly polarized luminescence (CPL) by which it differs from circular dichroism (CD), which should not be ignored particularly the orientational distribution of the molecules. In the case of CPL it is the orientational distribution of the population of excited molecules that is relevant, and it may be dramatically different from the orientational distribution of the population of the molecules in the ground state, which is relevant to CD measurements.

Journal ArticleDOI
TL;DR: In this article, it was shown that the dichroism induced in an optically active fluid by an electrostatic field is an even function of the field strength, and that the linear effect predicted in a paper in this journal for a fluid comprised of molecules of C n symmetry partially oriented by the field is therefore not likely to be found.

Journal ArticleDOI
TL;DR: In this article, the angular correlation of discrete gamma-ray transitions in coincidence with the light fragments detected at 35 was measured for the reaction 100-MeV /sup 16/O + Ni.
Abstract: The circular polarization of the energy-integrated ..gamma..-ray spectra and the angular correlation of discrete ..gamma.. transitions in coincidence with the light fragments detected at 35 were measured for the reaction 100-MeV /sup 16/O + Ni. A large nuclear spin polarization and at least 80% negative-angle scattering are deduced for deep-inelastic events. The decrease of the circular polarization observed at Q 4 : 30 MeV is ascribed to increasing positive angle contributions to the cross section.

Journal ArticleDOI
TL;DR: In this article, the circular polarization of γ-rays froin the capture of polarized neutrons in isotopically enriched targets of 42, 44 Ca, 46 Ti, 56, 58 Fe and 64 Ni has been measured.

Book ChapterDOI
TL;DR: This chapter provides a Description of the special techniques required for measurements of vacuum ultraviolet circular dichroism (VUCD) and a description of the information that can be obtained from VUCD measurements that are not obtainable from circular dichROism (CD) measurements at longer wavelengths.
Abstract: Publisher Summary This chapter provides a description of the special techniques required for measurements of vacuum ultraviolet circular dichroism (VUCD) and a description of the information that can be obtained from VUCD measurements that are not obtainable from circular dichroism (CD) measurements at longer wavelengths. Inasmuch as the first measurements of CD in the vacuum ultraviolet were made only a few years ago, an historical reference ought to be permitted to place that development into a larger perspective. The fundamental principles of optics necessary to know to understand the phenomenon of circular dichroism are described very often. At present, there is no commercially available instrument that allows CD measurements at wavelengths lower than about 185 nm. In commercial instruments, ammonium or potassium dihydrogen phosphate (ADE KDP) is used to produce alternately right and left circularly polarized light through the application of the Pockels' effect, but ADP and KDP are not transparent far into the vacuum ultraviolet region.



Journal ArticleDOI
TL;DR: In this paper, the excitation process of energetic ions, reflected at grazing angles from a metallic target, is assumed to be an electron-loss-capture sequence, and the density operator at the time of the last capture is factorized into an anisotropic part for the optical electron and an isotropic part for inner electrons.
Abstract: The excitation process of energetic ions, reflected at grazing angles from a metallic target, is assumed to be an electron-loss-capture-sequence. The density operator at the time of the last capture is factorized into an anisotropic part for the optical electron and an isotropic part for the inner electrons. Parentage approximation andLS-coupling then give the orientation for all levels of a supermultiplet. The circular polarized light, emitted during transitions from these levels, can be well fitted, with exception of lines fromL=0 terms. This shortcoming is removed by an extended model. This suggests that the parent ions, too, are oriented.


Journal ArticleDOI
TL;DR: In this paper, two-dimensional high-resolution observations of about 30 moving type IV bursts were used to compare the polarization structure of the radio sources high in the corona with the distribution of magnetic fields measured at the photospheric level.
Abstract: Two-dimensional, high-resolution observations of about 30 moving type IV bursts allow us to compare the polarization structure of the radio sources high in the corona with the distribution of magnetic fields measured at the photospheric level. Left- and right-handed circularly polarized moving type IV bursts are associated with active regions dominated by magnetic fields of plus and minus polarity respectively. The result suggests that the polarity of magnetic fields within the type IV source which moves high in the corona (≳ 1R ⊙ above the photosphere) is closely related to the polarity of local magnetic fields at the photosphere. The above relation between the sense of polarization and the polarity of magnetic field is contrary to what would be expected from the generally accepted synchroton hypothesis. One way of resolving this conflict is to postulate that the magnetic field within the radio source has the opposite polarity to that of the ambient magnetic fields.


Journal ArticleDOI
TL;DR: In this paper, it has been verified that the lowest excitonic molecule state of CuCl is composed of two-electron and two-hole states both of the composite spin angular momentum zero.
Abstract: The \(\varGamma_{1}\)-symmetry of the lowest excitonic molecule state of CuCl has been confirmed experimentally from the measurements of the giant two-photon absorption and resonance Raman scattering by using circularly polarized dye laser light. The giant two-photon transition is found to be forbidden for single beam of circularly polarized light while it is allowed for two beams of circularly polarized lights impinging in crystals from directly opposite directions. It has been verified that the lowest excitonic molecule state is composed of two-electron- and two-hole-states both of the composite spin angular momentum zero.

Journal ArticleDOI
TL;DR: In this paper, the authors analyzed 7 GHz bursts with a time constant of 100 ms and showed that the microwave fast component burst source might remain nearly stationary in relation to the polarizing medium, occupying the same position as the active center hot spot previous to the event.
Abstract: The ultimate definition of fast time structures superimposed on an impulsive solar microwave burst is limited by instrumental time resolution and sensitivity. We analysed 7 GHz bursts with a time constant of 100 ms. The fast time structures seem to be common to all events, although the resolution so far attained might still be smoothing out structures with finer scale. The polarization degree does not show corresponding fast changes. When the degree of circular polarization is referred to the burst's excess flux, it may show a slowly varying time development. When it is referred to the total active center contribution, the polarization degree might become nearly unchanged during the burst development. The polarization degree is set by the large scale magnetic field strength and morphology over the active center and the burst source. The present results suggest that the microwave fast component burst source might remain nearly stationary in relation to the polarizing medium, occupying the same position as the active center hot spot previous to the event. The absence of fast time structures in polarization degree indicate negligible fast changes in the large scale magnetic field which pervades the burst source. Slow changes in polarization degree are sometimes associated with the slow component of impulsive events, and might be representative of secondary accelerations interpreted in terms of trap models. We discuss qualitatively some energy conversion mechanisms based on turbulent processes which may account for the fast burst components.

Journal ArticleDOI
TL;DR: In this article, a multicolor photometry and polarimetry of AM Herculis was used to find correlations among polarization, flux, and color in the V and I bands in periodic and non-periodic (i.e., flickering) activity.
Abstract: Via simultaneous multicolor photometry and polarimetry of AM Herculis, we find correlations among polarization, flux, and color in the V and I bands in periodic and nonperiodic (i.e., flickering) activity. The primary minimum observed in both bands is accompanied by a blueward shift of the (B - R) color and a decrease in the absolute value of the percent circular polarization in the V band. Outside primary minimum, peaks of flickering activity tend to be associated with an increase in the absolute value of the circular polarization and the concurrent reddening of the (B - R) and (R - I) colors. The visual light curve of AM Her can be explained by a flickering, circularly polarized light source which is obscured at primary minimum, and is redder than the total system color in the URVRI bands.

Journal ArticleDOI
TL;DR: In this article, population and spin relaxation rates concerned with exciton luminescence and multiple LO-phonon emission lines were studied in ZnTe at 77 K by means of optical circular polarization correlation between the exciting and emitted lights.