Double Exponential Decay of Imprisoned Resonance Radiation

1971 ◽  
Vol 49 (1) ◽  
pp. 90-101 ◽  
Author(s):  
J. S. Deech ◽  
W. E. Baylis
Keyword(s):  
Exponential Decay ◽  
Linear Polarization ◽  
Incident Radiation ◽  
Average Degree ◽  
Resonance Radiation ◽  
Quantum Mechanical ◽  
Scattering Process ◽  
Double Exponential ◽  
Degree Of Coherence ◽  
Experimental Values

The decay of imprisoned resonance radiation in mercury has been studied using delayed-coincidence techniques. It is characterized by two exponentially decaying components, whose relative amplitudes depend on the direction of linear polarization of the incident radiation. When this direction makes an angle of 54.7° to the direction of observation, only one component is observed. Classical and quantum-mechanical theories are presented which show that the geometry of the scattering cell plays an important role at low atomic densities. Experimental values are presented for the average degree of coherence transferred in the scattering process and for the natural lifetime of the 63P1 state of mercury.

Exponential decay, recurrences, and quantum-mechanical spreading in a quasicontinuum model

1983 ◽  
Vol 28 (1) ◽  
pp. 32-39 ◽  
Author(s):  
P. W. Milonni ◽  
J. R. Ackerhalt ◽  
H. W. Galbraith ◽  
Mei-Li Shih
Keyword(s):  
Exponential Decay ◽  
Quantum Mechanical

scholarly journals Effects of internal mixing and aggregate morphology on optical properties of black carbon using a discrete dipole approximation model

2012 ◽  
Vol 12 (10) ◽  
pp. 26401-26434 ◽  
Author(s):  
B. Scarnato ◽  
S. Vahidinia ◽  
D. T. Richard ◽  
T. W. Kirchstetter
Keyword(s):  
Optical Properties ◽  
Black Carbon ◽  
Linear Polarization ◽  
Incident Radiation ◽  
Dipole Approximation ◽  
Approximation Model ◽  
Mixing State ◽  
Internal Mixing ◽  
Aggregate Morphology ◽  
Nm Range

Abstract. According to recent studies, internal mixing of black carbon (BC) with other aerosol materials in the atmosphere alters its aggregate shape, absorption of solar radiation, and radiative forcing. These mixing state effects are not yet fully understood. In this study, we characterize the morphology and mixing state of bare BC and BC internally mixed with sodium chloride (NaCl) using electron microscopy and examine the sensitivity of optical properties to BC mixing state and aggregate morphology using a discrete dipole approximation model (DDSCAT). DDSCAT predicts a higher mass absorption coefficient, lower single scattering albedo (SSA), and higher absorption Angstrom exponent (AAE) for bare BC aggregates that are lacy rather than compact. Predicted values of SSA at 550 nm range between 0.18 and 0.27 for lacy and compact aggregates, respectively, in agreement with reported experimental values of 0.25 ± 0.05. The variation in absorption with wavelength does not adhere precisely to a power law relationship over the 200 to 1000 nm range. Consequently, AAE values depend on the wavelength region over which they are computed. In the 300 to 550 nm range, AAE values ranged in this study from 0.70 for compact to 0.95 for lacy aggregates. The SSA of BC internally mixed with NaCl (100–300 nm in radius) is higher than for bare BC and increases with the embedding in the NaCl. Internally mixed BC SSA values decrease in the 200–400 nm wavelength range, a feature also common to the optical properties of dust and organics. Linear polarization features are also predicted in DDSCAT and are dependent on particle morphology. The bare BC (with a radius of 80 nm) presents in the linear polarization a bell shape feature, which is a characteristic of the Rayleigh regime (for particles smaller than the wavelength of incident radiation). When BC is internally mixed with NaCl (100–300 nm in radius), strong depolarization features for near-VIS incident radiation are evident, such as a decrease in the intensity and multiple modes at different angles corresponding to different mixing states. DDSCAT, being flexible on the geometry and refractive index of the particle, can be used to study the effect of mixing state and complex morphology on optical properties of realistic BC aggregates. This study shows that DDSCAT predicts morphology and mixing state dependent optical properties that have been reported previously and are relevant to radiative transfer and climate modeling and interpretation of remote sensing measurements.

Notizen: Quantum Mechanical Calculation of Collision Integrals for HD

1971 ◽  
Vol 26 (11) ◽  
pp. 1926-1928 ◽  
Author(s):  
W. E. Köhler
Keyword(s):  
Scattering Amplitude ◽  
Quantum Mechanical ◽  
Collision Term ◽  
Tensor Polarization ◽  
Collision Integrals ◽  
First Order ◽  
Relaxation Coefficient ◽  
Angular Momenta ◽  
Experimental Values ◽  
Good Agreement

The magnetic Senftleben-Beenakker effect of the viscosity is mainly determined by two collision integrals of the linearized quantum mechanical Waldmann-Snider collision term, viz. by the relaxation coefficient of the tensor polarization of the molecular rotational angular momenta and by the coefficient which couples the friction pressure tensor and the tensor polarization. Starting from a simple nonspherical potential for HD, the scattering amplitude is evaluated analytically in first order distorted wave Born approximation and the two collision integrals are calculated for room temperature. A fairly good agreement with experimental values is found.

The circulatory half-lives of α -profibrin and α-fibrin monomer, and comparisons with other fibrin(ogen) derivatives

2003 ◽  
Vol 89 (01) ◽  
pp. 48-52 ◽  
Author(s):  
Patricia DiBello ◽  
John Shainoff
Keyword(s):  
Vascular Disease ◽  
Exponential Decay ◽  
Half Life ◽  
Decay Curve ◽  
Human Fibrinogen ◽  
Extravascular Space ◽  
Plasma Decay ◽  
Exponential Decay Curve ◽  
Fibrin Monomer ◽  
Double Exponential

SummaryPrevious studies showed that α-fibrin monomer (lacking both A-fibrinopeptides, FPA) is normally cleared from the circulation before it assembles into a clot. Recent studies indicate that substantial quantities of an intermediate, α-profibrin lacking only one of the two FPA are produced in the course of conversion of human fibrinogen to fibrin. Since clearance of the α-fibrin monomer is saturable and receptor mediated, the extent to which α-profibrin or other fibrin(ogen) derivatives might compete for monomer uptake was deemed important. We compared plasma decay of injected human α-fibrin, fibrinogen, and α-profibrin in rabbits using rabbit anti-human fibrinogen for assays. The circulatory half-life of human α-fibrin monomer was short (t1/2 = 2.3 h) and followed a simple exponential decay curve, as anticipated from clearance of rabbit α-fibrin. It was absorbed as fast as it permeated the extravascular space with no redistribution. Human fibrinogen had a long half-life (t1/2 = 39.5 h), calculated from the double exponential plasma decay curves (redistribution + catabolism) observed over 28 h. The α-profibrin had an intermediary half-life (t1/2 = 11 h) determined from double exponential decay curves. Since redistribution accompanied the slow clearance of α-profibrin, its binding by the fibrin receptor(s) must be weak, probably too weak to compete with the clearance of α-fibrin monomer. The initial production of α-fibrin monomer is only partially dependent on prior formation of α-profibrin, as recently shown. Thus, it is the slow clearance and the weak competition from α-profibrin that underlie the occurrence of substantial levels of α-profibrin unaccompanied by detectable levels of α-fibrin monomer in many subjects with vascular disease.

Elliptically Polarized Natural Modes in Pulsar Magnetospheres

1982 ◽  
Vol 4 (4) ◽  
pp. 365-370 ◽  
Author(s):  
Michelle C. Allen ◽  
D.B. Melrose
Keyword(s):  
Circular Polarization ◽  
Linear Polarization ◽  
Strong Support ◽  
Position Angle ◽  
Average Degree ◽  
Pole Model ◽  
Magnetic Pole ◽  
Pulse Profile ◽  
Linearly Polarized ◽  
High Degree

The most obvious feature of the polarization of the radio emission from most pulsars is the rotation of the plane of linear polarization across pulses. The original interpretation of this in terms of the magnetic pole model (Radhakrishnan 1969, Radhakrishnan et al. 1969, Radhakrishnan and Cooke 1969) accounts for the variation of position angle extremely well for some pulsars (e.g. Manchester and Taylor 1977, Manchester 1978). Conversely, this provides strong support for the magnetic pole model for pulsar emission. It also suggests that the emission is basically linearly polarized as implied by virtually all proposed emission mechanisms, e.g. the reviews by Ginzburg and Zheleznyakov (1975) and Arons (1979). However, there are two features of the polarization which require a separate explanation. First, some pulsars have a moderately high degree of circular polarization, even in the integrated pulse profile (Manchester 1971, Lyne, Smith and Graham 1971). In some pulsars the average degree of circular polarization can exceed the average degree of linear polarization, e.g. in PSR 0835-41 and 0959-54 (McCulloch et al. 1978). Second, some pulsars exhibit the phenomenon of transitions between orthogonal elliptical polarizations (Manchester, Taylor and Huguenin 1975, Backer, Rankin and Campbell 1976, Cordes and Hankins 1977, Cordes, Rankin and Backer 1978). In many pulsars the orthogonal polarizations have substantial circular components, e.g. in PSR 1133 + 16 (Manchester et al. 1975) and PSR 2020 + 28 (Cordes et al. 1978).

ANALYSIS OF MELTING FOR ALKALI EARTH AND ALKALI OXIDES BASED ON THE DIFFUSIONAL FORCE THEORY

2004 ◽  
Vol 18 (21n22) ◽  
pp. 1101-1107 ◽  
Author(s):  
QUAN LIU ◽  
LI-RONG CHEN
Keyword(s):  
Quantum Mechanical ◽  
Repulsive Potential ◽  
Ionic Model ◽  
Alkali Earth ◽  
Melting Temperatures ◽  
Quadrupole Interactions ◽  
Quantum Mechanical Treatment ◽  
Alkali Oxides ◽  
Experimental Values ◽  
Good Agreement

An analysis of the melting alkali earth and alkali oxides is presented using the concept of diffusional force. The calculations are performed by developing an ionic model based on Harrison's quantum mechanical treatment of overlap repulsive potential which takes into account the interactions up to second neighbors. Van der Waals dipole–dipole and dipole–quadrupole interactions calculated by more accurate methods are also included in the model. Using the formula by Fang, derived on the basis of thermodynamic analysis, the values of interionic distances for 8 alkali earth and alkali oxides at melting have been obtained. A simple model for melting is developed based on the diffusional force models. The values of Tm thus obtained are found to show fairly good agreement with experimental values of melting temperatures.

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