Showing papers on "Circular polarization published in 1970"

Polarization Dependence of the Two-Photon Absorption of Tumbling Molecules with Application to Liquid 1-Chloronaphthalene and Benzene

Abstract: The two‐photon absorption cross section δ for photons of any polarization (linear, circular, or elliptical) is averaged over all orientations of the absorbing molecule. The result is given by 〈δ〉 = δFF + δGG + δHH, where δF, δG and δH are molecular parameters and F, G, and H are simple functions of the polarization vectors. It is shown how the δ's may be calculated from theory and also how they may be measured by experiment. Experiments using only linearly polarized light are insufficient to determine all three δ's; hence, circularly polarized light will play an essential role in this spectroscopy. For absorption of two linearly polarized photons with angle θ between their polarization vectors, the angular dependence is 〈δ〉 = A + Bcos2θ, where A and B are simple combinations of the δ's. We obtain two exact symmetry rules which permit allowed two‐photon transitions of different symmetries to be distinguished. For transitions from totally symmetric ground states the rules are: (1) If the excited state transforms like xy, yz, or zx, then δF = 0. (2) If the excited state transforms like x2, y2, or z2, then δG = δH. In cases of near resonance, when a single intermediate state dominates the formula for the cross section, we show that δF = δH, and that linearly polarized light suffices for a complete investigation. These results are applied to liquid 1‐chloronaphthalene. We find two allowed two‐photon transitions which are assigned 1B1g (perpendicular nodes) at 37 700 cm−1 and 1 Ag (total symmetry) at 42 600 cm−1. This is in reasonable agreement with theoretical predictions of other authors. We have also examined the region of the second excited singlet of benzene, near 6.2 eV. We were not able to detect any two‐photon absorption, setting an upper limit of about 10−51 cm4·sec/photon·molecule on its 〈δ〉. This leads to an unequivocal assignment of 1B1u for this state according to calculations of Jortner. In an Appendix we examine the effect of “hot spots” in the laser beam on the observed cross sections. We show that the elimination of the hot spots is of some importance, contrary to a statement of other authors.

Temperature-dependent tilt angle in the smectic C phase of a liquid crystal

Abstract: Liquid crystal smectic C phase temperature dependent tilt angle, using conoscopic observation and circularly polarized light

Differential Scatter of Left and Right Circularlay Polarized Light by Optically Active Particulate Systems

Abstract: Because of the many heterogeneous systems which are of interest to the chemist and biochemist, the problems of distortions in circular dichroism patterns have been investigated. Specifically in this communication it is shown with a relatively well-characterized particular system (a suspension of α-helical poly-L-glutamic acid) that there is a measurable differential scatter of left and right circularly polarized light by suspensions of the optically active particles. This is a specific example of Perrin's assertion in 1942 (Perrin, F., J. Chem. Phys., 10, 415 (1942)) that the polarization characteristics of scattered light would differ depending on whether or not the scattering particle was optically active. Differential scatter is included with the concentration obscuring effects to demonstrate that distorted circular dichroism spectra on poly-L-glutamic acid suspension can be calculated with satisfying accuracy. The approach should be applicable to correcting the circular dichroism spectra for the many particles of biological interest, e.g., membranes, viruses, mitochondria, and insoluble proteins and polypeptides, and for small crystals in an effort to answer the crystal solution problem.

Pulsar NP 0532: properties and systematic polarization of individual strong pulses at 430 MHz.

Abstract: This paper reports further detailed measurements of strong radio pulses from the pulsar NP 0532 in the Crab nebula, recorded at Arecibo

Pulsar NP 0532: average polarization and daily variability at 430 MHz.

Abstract: MEASUREMENT of optical polarization has of course been limited to NP 0532. The optical radiation in both the main pulse and the interpulse, averaged over many pulses, is weakly linearly polarized (∼15 per cent) with a position angle which rotates in a manner akin to that in PSR 0833–45 (refs. 1 and 2). The polarization properties, as well as the total intensity and pulse shape, seem to be time-dependent, however3. Circular polarization is absent.

On polarimetry in solar active regions

Abstract: Measurements of the circular polarization V in different lines show that the deduced magnetic field strength and flux are systematically influenced by variations of the line absorption coefficient from photosphere to spot and faculae.

Magnetoemission from Incandescent Bodies

Abstract: We report experimental detection of a newly recognized, spectrally diffuse circular polarization in light from various incandescent bodies in a magnetic field. Polarization fractions of ${10}^{\ensuremath{-}5}$ -${10}^{\ensuremath{-}4}$ are seen at 1.5\ensuremath{\mu}m in a 25-kG field, roughly conforming with a very simple theory.

Circular Polarization of Quasars at λ49 Cm

Abstract: IT has been suggested that radio sources emitting by the synchrotron process may show a small degree of circular polarization, as well as the well known linear polarization1,2. Previous measurements at shorter wavelengths have failed to detect circular polarization3,4 or have been near the limit of measurement5,6.

80 MHz Observations of the Movement of a Type IV Source out to 6 R

Abstract: A moving type IV radio source on 1970 March 21 was observed with the 80 MHz Culgoora radioheliograph to move out to a distance of p = 6 (where p = R/R ®). Starting as a single source of complex shape it later developed strong circular polarization (> 90% R.H.) and separated into components which retained the same polarization. The source appeared soon after a prominence eruption (or flare spray) from which some of the ejected matter travelled in the same direction as, and with a velocity close to, that of the radio source.

Radiative opacities and compton scattering in strong magnetic fields.

Abstract: Magnetic field effects on Compton scattering and radiative opacity, considering longitudinal and transverse propagation with circular polarization

Method and apparatus for control of light transmission through an anisotropic medium

Abstract: An electronically tunable acousto-optic filter is disclosed of the type wherein light of a first polarization is diffracted on an acoustical wave traveling collinearly of the light in an anisotropic birefringent medium to shift the polarization of the light from a first polarization to a second polarization. The intensity of the acoustic wave in the birefringent medium is varied to vary the ratio of the intensity of the light diffracted from the first polarization into the second polarization. The band pass of the acousto-optic filter is electronically tuned by varying the frequency of the acoustic wave in the birefringent medium. The acousto-optic device may be employed as an attenuator, chopper, or modulator for light.

Acousto-optic light spectrum analysis

Abstract: An acousto-optic light spectrum analysis method and apparatus is disclosed. A linearly polarized unknown light beam to be spectrum analyzed is collinearly diffracted on an acoustic wave in an optically anisotropic medium to diffract light of the first linear polarization and of a frequency related to the frequency of the acoustic wave into light of a second polarization. The diffracted unknown light beam is polarization analyzed to separate the light of the second polarization from the light of the first polarization. The frequency of the acoustic wave is swept and the light of the second polarization is detected as a function of the sweep to obtain a spectrum analysis of the unknown light beam. The output spectrum of the unknown light beam is calibrated by switching a known light source through the acousto-optic system for calibration of the output spectrum.

A Synchrotron Model for the Decimetric Rradiation of Jupiter

Abstract: The two-dimensional distribution of intensity and polarization has been calculated for the synchrotron radiation from electrons trapped in a dipolar magnetic field around a planet. From formulas recently published by Legg and Westfold, the circular polarization is included. The integrated data from these maps are used to suggest models with two thick belts of electrons to account for the decimetric radiation from Jupiter.

Beitrag zur Kernspektroskopie an 36 Cl, 90 Y und 40 K durch Messung der Polarisation von γ-Strahlung nach Neutroneneinfang

Abstract: The circular polarization ofγ-rays following the capture of polarized thermal neutrons in nuclei was measured. The degree of polarization confirmed the spin 2+ for the 0.777 MeV level of90Y and the spin 0− or 3− for the 0.029 MeV level of40K. Further theE2/M1 mixing ratio of the 8.58 MeV decay to the ground state of36Cl was measured.

Messung der Zirkularpolarisationskorrelation bei Fe 59 , Sb 124 und Ru 103

Abstract: TheΒ-γ circular polarization asymmetry for three nuclides has been measured using a special polarimeter developed at Karlsruhe. The results of the measurements are Nuclid A Transition Fe59 −0158±0.007 β0.47−γ1.10 MeV Sb124 +0.278±0.013 β0.62−γ1.69 MeV Ru102 −0.107±0.011 β0.22−γ0.50 MeV

Improved polarization holography

Abstract: Using circularly polarized light, high‐quality holograms can be obtained, containing information on the polarization characteristics of the object. A theoretical derivation and some experimental demonstrations are given.

Far-infrared laser action using compound grating Fabry-Perot resonators

Abstract: A water vapor laser has been operated with a subsidiary grating Fabry-Perot resonator replacing one end mirror Double-wavelength operation was obtained Single-wavelength operation was obtained with strong rejection of shorter wavelength radiation, a variable effective reflectivity of the end mirror, and control of polarization characteristics of the cavity, allowing linear or circular polarization

Apparatus for determining the position coordinates of a point relative to a reference point

Abstract: For measuring the coordinates of one point relative to a reference point a linearly polarized laser beam from the reference point impinges upon a circular polarization filter of a measuring device at the point to be measured. The filter which consists of two semicircular filters whose directions of polarization are perpendicular to each other has a larger diameter than the beam. The filter or the polarization plane of the beam rotates about the center of the filter and a lens focuses the beam passing through the filter onto a photoelectric receiver to produce a current. If the filter is centered relative to the beam a direct current is only produced; if not, an AC component is generated. A phase-sensitive rectifier coupled to the receiver produces an electric signal whose phase and amplitude represent the angular position of the point of impingement of the beam relative to the center of the filter. The signal may be fed to an indicating device for indicating the coordinates represented thereby and/or may be fed to means, such as servomechanism, operable to move the measuring device until the filter is centered with the beam.

Polarization effects in holography.

Abstract: Abstract : Holograms were made of the reflected beam from a simple object which had its angle of polarization varied from parallel to orthogonal in relation to the polarization in the reference beam. The brightness of the light diffracted into the image by the hologram was measured with a Spectra-Pritchard photometer. The results are presented in graphical form. It was concluded that polarization phase angles should not exceed about fifteen degrees when calculating the beam ratios for holograms. (Author)

Polarization changes with time during solar microwave impulsive bursts

Abstract: The evolution with time of circular polarization π(t) from solar bursts at 7 GHz presents, in the majority of cases, a polarization degree peak before the maximum flux time. The subsequent evolution of π(t) is continuous and usually increasing. The changes could be caused by superimposed polarization effects, due to the fast emissive electrons (dominant in the first phase), and to the propagation effects caused by the coronal condensation where the event occurred (dominant in the second phase). In an approximate approach, π(t) is connected to the movement of the source in the second phase, being qualitatively sound, but limited to the lack of knowledge on acceleration processes and on magnetic field topology in the active region where the flares take place.

Pulsar NP 0532: Polarization of Strong Pulses at 430 MHz as seen with 300 kHz Bandwidth

Abstract: THE polarization properties of strong pulses from NP 0532 have been measured by Graham, Lyne and Smith1, who used a 330 kHz bandwidth corresponding to a time resolution of about 2 ms; and by Heiles, Campbell and Rankin2, who used a 10 kHz bandwidth corresponding to a time resolution of 120 µs. The former authors measured large linear polarization; they did not know which pulse component was responsible for the strong pulses, but they suspected the precursor because of its high average linear polarization3. We measured systematic circular polarization in the strong main pulses, and proposed that the differences in results might be due to the difference in observing bandwidth.