摘要:

Excitation can move from Tb to Eu at 4.2°K by processes involving exchange even though the electronic transitions concerned are not matched in energy. At 295°K, thermal effects cause an overlap permitting dipole‐dipole transfer to occur. Transfer to Eu may be enhanced by excitation migration from more remote Tb ions to those closer to Eu at 295°K. This migration is not effective at 4.2°K, and hence appears to require thermal activation.

ISSN:0003-6951    

DOI:10.1063/1.1754738

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

The selection of a single mode‐locked pulse from aQ‐switched Nd+3‐doped glass laser is described. Mode‐locking is achieved by self‐mode‐locking the laser using a bleachable dyeQswitch. Selection of a single pulse is achieved by means of a modification of the pulse transmission mode described by Vuylsteke.

ISSN:0003-6951    

DOI:10.1063/1.1754739

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

InAs thin films have been prepared by coevaporation. Hall mobilities up to 8000 cm2/V‐sec have been obtained in films 3000‐A˚ thick, and 3000 cm2/V‐sec in 1000‐A˚ films. Field‐effect transistors have been fabriacted of such films, exhibiting good saturation in both enhancement and depletion modes of operation. Field‐effect mobilities of 1800 cm2/V‐sec, transconductances of 10,000 &mgr;‐mhos and gain‐bandwidth products of 8 MHz were obtained in devices with a 100‐&mgr; source‐drain spacing. Performance in the GHz region is predicted for devices of suitable geometry.

ISSN:0003-6951    

DOI:10.1063/1.1754740

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

LEED observations between 200–1000 V on the clean (111) face of silicon indicate a set of diffuse rings which, contrary to normal behavior of diffraction features, move outward from the normal with decreasing electron wave‐length. The origin of these rings is determined to be multiple scattering from nearest‐neighbor pairs. Estimates of the electron mean free path average about a value larger than the nearest‐neighbor distance but smaller than the separation of nearest‐neighbor pairs in the (111) direction. The rings appear to be associated with Kikuchi patterns which are observed down to 400 V.

ISSN:0003-6951    

DOI:10.1063/1.1754741

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

Whisker crystals and related filamentary and spherical shapes grow at the solder terminations of thin‐film resistors when the circuits carry excessive direct current. The growths have been observed in most instances near the positive termination. With tin‐lead solder the growths at the positive termination are predominantly tin. Whisker crystals are often single. Studies show that electrotransport plays a role in the growth.

ISSN:0003-6951    

DOI:10.1063/1.1754742

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

Work function measurements have been carried out on the densely packed (110) plane of tungsten. Field‐ion microscope techniques have been used to obtain atomically perfect single‐crystal (110) planes. Field‐electron emission energy distributions have been combined with Fowler‐Nordheim measurements to give work function values at 77°K. The electrostatic patch fields which exist at the measured surface result in corrections which tend to increase the work function value. The measurements reported here are not corrected for patch fields and range in value from 7.1 eV to 8.7 eV for the (110) plane. Future measurements will employ a newly developed technique involving a family of energy distribution plots which eliminates the correction for patch fields.

ISSN:0003-6951    

DOI:10.1063/1.1754743

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

Ultrathin CdSe lasers of variable mode spacing, including the special case of single‐mode output, are described. A simple experimental procedure for volume optical excitation of a thin semiconductor sample is described.

ISSN:0003-6951    

DOI:10.1063/1.1754744

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A peak in the critical current vs magnetic field characteristic of Nb−25% Zr has been produced during a low‐temperature (∼30°K), 15‐MeV deuteron irradiation (1017deuterons/cm2). The peak occurs at fields near the upper critical field,Hc2; essentially no changes were observed at lower fields. Annealing at 77°K produced almost no change in the peak whereas it nearly disappeared after annealing at 300°K. It is concluded that this peak is a bulk effect associated with radiation‐induced defects of intermediate size and complexity which are effective pinning centers nearHc2, but are too ``weak'' to affect the critical current at lower fields. A number of possible mechanisms are briefly discussed.

ISSN:0003-6951    

DOI:10.1063/1.1754745

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

Single high‐power output pulses from aQ‐switched ruby laser are focused onto thin copper crystals. Diffraction‐contrast transmission electron microscopy reveals that so‐called black spot defects are introduced in the samples, within the laser‐produced crater areas. These defects are similar to those observed, for example, in neutron‐irradiated copper samples. They cause a marked increase in hardness at and near the crystal surface.

ISSN:0003-6951    

DOI:10.1063/1.1754746

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

The parallel‐pumped spin‐elastic wave instability and ferromagnetic resonance were used to measure the dispersion and losses of &pgr;/2 spin waves in high‐purity, single‐crystal GdIG at low temperatures. The spin wave dispersion constant varies more rapidly with temperature than predicted by molecular field theory and the resonance losses are only a factor of three greater than those for YIG.

ISSN:0003-6951    

DOI:10.1063/1.1754747

出版商:AIP    

年代:1966

数据来源: AIP