摘要:

A density matrix formulation of the interaction of radiation with bands of pressure‐broadened overlapping spectral lines is described which includes the effects of interaction between neighboring lines due to collisions. A measurement of the abosrption coefficients at the centers of several lines of the 10.6‐ and 9.4‐&mgr;m bands of CO2for CO2and mixtures of CO2and N2and He at absolute pressures to 18 atm is reported. The calculated spectra of these bands are given for the two limiting forms of overlapping line theory: one which maximizes line interaction and another which neglects it, calculating the spectra as sums of Lorentzian‐shaped lines. The data are shown to be in good agreement with the theory which maximizes the line interaction.

ISSN:0021-8979    

DOI:10.1063/1.325296

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

High pressure was used to change the viscosity isothermally for the measurement of polarization of fluorescence of small fluorescent molecules in solution. A new technique, necessary for the measurements, as well as a new instrument to perform them, are described and discussed. Although the apparatus is not well suited for determining absolute polarization values, it is quite accurate in detecting changes in polarization due to change in pressure. Independent readings of polarization at 1 atm were therefore obtained using a different instrument. For the sample system, quinine sulfate in isobutanol, there is good agreement between the data obtained by pressure variation and those obtained by temperature variation. The extension of the method to study polymers and proteins in solution and its advantages over previous methods are also discussed.

ISSN:0021-8979    

DOI:10.1063/1.325297

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Excitation‐transfer cross sections have been measured for Penning and charge‐transfer reactions in He‐Ca, He‐Sr, Xe‐Ca, and Xe‐Sr discharges. In low‐current low‐pressure discharges of helium, excitation transfer to ionic levels of calcium and strontium was found to be dominated by collisions with 23Shelium metastables with measured cross section &sgr; (He 23S–Ca) =4.1×10−15cm2and &sgr; (He 23S–Sr) =1.6×10−15cm2. In xenon discharges, charge‐transfer cross sections between xenon ions and calcium and strontium atoms, &sgr; (Xe+‐Ca) and &sgr; (Xe+‐Sr), were measured to be 2.2×10−16and 2.3×10−16cm2, respectively.

ISSN:0021-8979    

DOI:10.1063/1.325298

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The effect of an insulator coating on the plasma electrode of a duoPIGatron ion source on ion‐beam optics was examined theoretically and experimentally. The effect of a preacceleration potential, applied between the insulated electrode and the target cathode of the source plasma, on ion optics was also examined. A principal result is that this electrode arrangement with precel gives a much lower beam divergence than the same arrangement without precel. Detailed comparisons between the data and calculations are presented.

ISSN:0021-8979    

DOI:10.1063/1.325299

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The levitation forces on metal spheres in magnetic fields of axial symmetry are derived theoretically. Criteria for stability of the center of mass are obtained. It is shown for nonmagnetic samples that the desirable coil configurations are those which provide a constant field gradient along the symmetry axis. The formalism is applied to model coils of axial symmetry as an approximation to real spiral coils. An exact formula is derived for the axial component of the magnetic field on the axis of a spiral coil wound on the surface of a cone, and the transverse fields are evaluated approximately.

ISSN:0021-8979    

DOI:10.1063/1.325300

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A new technique for the determination of the Raman cross section by means of the enhancement of CARS signal is presented. This technique was tested on deuterium, and the result obtained is in good agreement with the literature value.

ISSN:0021-8979    

DOI:10.1063/1.325301

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The physical mechanisms of the breakdown of carrier confinement are considered using both the thermionic‐emission and diffusion models. It is shown that, for most practical AlGaAs/GaAs DH lasers, the diffusion current is responsible for carrier leakage. The thermionic emission of minority carriers is important when the confinement barrier or the mobility is very large. The theory presented here is also applicable to structures other than the AlGaAs/GaAs laser.

ISSN:0021-8979    

DOI:10.1063/1.325302

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

As‐grown single‐crystal ruby fibers have been operated continuously as end‐pumped lasers, in air at room temperature, without active cooling. The fiber laser elements were about 40 &mgr;m in diameter and 0.25 cm long, with a Cr3+concentration of 0.02&percent;. The pump source was a Kr laser. Continuous operation was in a single transverse mode at one to five longitudinal resonant frequencies, the observed relaxation oscillations were regular and periodic, and the output was plane polarized. Fiber growth is described, and both transient and steady‐state heating effects in the laser due to pump absorption are discussed.

ISSN:0021-8979    

DOI:10.1063/1.325303

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Optical‐gain spectra from ZnO at 300 and 1.8 K have been recorded by a new modulation technique. The gain is extracted from amplified spontaneous emission by modulation of the excitation length and synchronous detection. The method is particularly suited for measuring gain coefficients in the range −100<g<500 cm−1. The observed gain spectra from ZnO are interpreted in terms of exciton‐exciton collision processes (300 K) and excitonic molecule transitions (1.8 K).

ISSN:0021-8979    

DOI:10.1063/1.325304

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

An investigation into the effects of temperature on degradation mechanisms in GaAs/GaAlAs DH lasers has been carried out. A mechanism (or mechanisms) independent of stimulated light levels is found to be relatively insensitive to temperature. This suggests that a residual failure mechanism may be associated with defect motion being enhanced by nonradiative recombination. A statistical analysis of the lifetest results and photoluminescence studies of lifetested devices suggest that there may be different mechanisms in operation at different temperatures. Thus, great care must be exercised before using conventional extrapolation techniques to predict laser lives at room temperature.

ISSN:0021-8979    

DOI:10.1063/1.325305

出版商:AIP    

年代:1978

数据来源: AIP