摘要:

The observation of electronic energy transfer to XeO(1&Sgr;+) from xenon atoms excited by two‐photon absorption is reported. Electronically excited xenon atoms in the 5p56pconfiguration are produced through two‐photon excitation at 248.4 nm (KrF*). Subsequent energy transfer from excited rare‐gas atoms to N2O leads to the appearance of XeO(1&Sgr;+), which is identified by the detection of its characteristic green emission band. These measurements are in accord with estimates of the relevant two‐photon amplitudes for Xe and N2O. Kinetic studies utilizing these techniques provide a flexible method for the study of selective excitation and energy transfer in a wide class of atomic and molecular materials.

ISSN:0021-8979    

DOI:10.1063/1.325127

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

An oven has been designed and built for the production of metal microcrystals via nucleation and growth of the metal vapor in an inert‐gas atmosphere. It has a flowing‐argon double‐orifice sampling system producing a supersonic free‐jet mixture which crosses a 40‐keV electron beam. Debye‐Scherrer diffraction patterns are obtained from the metal cluster samples which range in size from 40 to 95 A˚ in diameter with estimated concentrations of 1012–1013cm−3at the electron beam location. The average cluster size produced in the oven for all three metals studied correlated well with the product of oven pressure times metal evaporation temperaturep0T0m. Asp0T0mincreases, average size increases and cluster concentration decreases, in qualitative agreement with other metal evaporation research and with nucleation studies of vapor–inert‐gas expansions in supersonic nozzles. Analyses of the diffraction patterns reveal changes in crystal structure from that of the bulk in the neighborhood of 50–60 A˚ in diameter (2000–4000 atoms per cluster). The differences are most pronounced in indium which changes from tetragonal to face‐centered cubic as the size decreases. Cluster temperatures at the electron beam location have been estimated from Debye‐Waller factors, from extrapolation to bulk structure, and from calculated values of the argon‐gas temperature in the free jet. The three methods yield consistent results, and the hotter the clusters are prior to the free‐jet expansion, the greater is the temperature difference between the clusters and the argon gas when the mixture becomes collisionless (i.e., no further change in the temperature of gas or custer).

ISSN:0021-8979    

DOI:10.1063/1.325128

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

High‐energy charged particles emit synchrotron‐Cˇerenkov radiation under the joint action of external magnetic fields and ambient media. The angular and spectral characteristics of this radiation have been derived by classical and quantum‐mechanical methods. The experimental significance of the angular distribution—particularly features associated with striations—are considered in some detail.

ISSN:0021-8979    

DOI:10.1063/1.325129

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A closed‐form solution to the central problem of the steady linear motion of an arbitrary current distribution past materials of constant permeability is presented. The application of the Green’s function technique to the field equations yields integral representations of the induction, eddy currents, and electromagnetic forces. Due to interface coupling of the boundary conditions along the surface of the conductor, Green’s functions are shown to satisfy integral equations. In the case of a conducting slab, explicit solutions for the Green’s functions are derived. Application to magnetic levitation and the calculations of forces on moving coils are developed. Results are compared with experimental drag measurements.

ISSN:0021-8979    

DOI:10.1063/1.325130

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A simple photopreionization‐stabilized waveguide laser is energized effectively by fast Blumlein‐type pulsers and operates at pressures of up to 13 atm. The laser has an active plasma volume of ∼0.2 cm3and provides 20 ns gain‐switched pulses with beam energies of 10 mJ. The maximum pressures and beam energies are more than an order of magnitude higher than those published previously; the peak power is enhanced by two orders of magnitude.

ISSN:0021-8979    

DOI:10.1063/1.325131

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Energy in a laser beam can be transferred to a solid and increase its thermal energy. In a series of experiments, this thermal coupling has been investigated for pulsed CO2laser beams. Target material, air pressure, focal spot size, and laser pulse separation time were varied. A feature often seen is an enhancement of the thermal coupling process above a fluence or intensity threshold. A method for the determination of the spatial profile of the heat absorbed by the target using a single on‐axis thermocouple is presented. For the focal spot size and other conditions in these experiments, this technique shows a heating profile with a width much larger than the focal spot width.

ISSN:0021-8979    

DOI:10.1063/1.325132

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A surprisingly long delay time (of the order of 10 &mgr;sec) is found necessary for maximum enhancement of the output power and energy from the main pulse of a 0.1‐liter‐volume Blumlein‐driven XeF excimer laser when another fast‐discharge pulse of about 0.1‐&mgr;sec duration and 10&percent; of the main discharge energy is used to preionized or otherwise ’’precondition’’ the gas mixture. At such optimal timing, a factor‐of‐5 enhancement of the UV laser output (3510<&lgr;<3537 A˚) has been observed in a He : Xe : NF3mixture at an overall generation efficiency of 1.3&percent;.

ISSN:0021-8979    

DOI:10.1063/1.325133

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The optical and magneto‐optical properties of crystals of Hg1−xCdxTe (x=0.37) have been measured over the CO2laser wavelength region. The absorption edge of this composition occurs at about 3.2 &mgr;m, and the Faraday rotation consists of interband and intraband components. The latter is very large inn‐type material due to the small electron effective mass (0.052). The figure of merit ofn‐type material is about 1.0 deg/kOe at 10.6 &mgr;m. Optical‐damage studies give a damage threshold of 160 MW/cm2, indicating application to high‐power laser isolator devices.

ISSN:0021-8979    

DOI:10.1063/1.325109

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A passive aperture‐scalable device is described which provides high contrast enhancement of a laser pulse over baseline optical noise while maintaining efficient net transmission of the principal laser pulse. The technique, which is based upon the nonresonant phenomenon of self‐induced ellipse rotation, is capable of providing effective gain isolation for virtually any high‐power laser system. The constrast enhancement capabilities of the device are demonstrated experimentally using a single ultrashort laser pulse obtained from a cavity‐dumped passively mode‐locked Nd : glass laser. In addition, a discussion is given concerning the ability of the device to temporally compress or stretch the optical pulse.

ISSN:0021-8979    

DOI:10.1063/1.325110

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

We report on the characteristics of active‐passive mode‐locked phosphate‐glass oscillators. These highly reliable oscillators operate at 1.054 &mgr;m and are characterized by the absence of satellite pulses for pulse durationstp≳80 psec. They have very high peak‐to‐background contrast of 107to 108. Transform‐limited pulse widths between 80 and 600 psec are reliably generated using a pair of intracavity etalons. The reproducibility of the pulse durations is better than ±10&percent;, that of the pulse‐train maximum about ±10 to 20&percent;. Single‐pulse selection with ±5&percent; amplitude fluctuation has been achieved with threshold‐pulse selectors. For pulses shorter than 50 psec, satellite pulses are occasionally observed. A theoretical explanation for this observation is given.

ISSN:0021-8979    

DOI:10.1063/1.325111

出版商:AIP    

年代:1978

数据来源: AIP