摘要:

An optical system for rapid routine pressure measurement is described which utilizes a pressure shift in the sharpR‐line fluorescence spectrum of ruby or similar materials. The system, which consists of a standard polarizing microscope and a 1/4 m monochromator with associated photodetection system, is used with the diamond‐anvil pressure cell, but can be employed with suitable modification in any pressure system which has optical access. The precision of the pressure measurement in a hydrostatic environment up to 100 kilobar is 0.5 kilobar using ruby as the pressure sensor. This precision is better than the accuracy of the present pressure scale above 40 kilobar. The merits of fluorescent materials other than ruby as pressure sensors are also discussed. A description of a Waspaloy diamond cell with some modifications in design is given. This improved cell and associated techniques extends the pressure range in gasketed systems up to 200 kilobar at room temperature and to moderate pressures at 700° C.

ISSN:0034-6748    

DOI:10.1063/1.1685943

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

We report a high sensitivity, near‐infrared circular dichroism (CD) instrument. CD is measured by the standard modulation method; phase modulation is provided by an Infrasil quartz photoelastic modulator. The spectral range 0.8–3.0 &mgr; is spanned. Incorporation of a superconducting magnet allows magnetic circular dichroism (MCD) measurements to be made. The natural CD of nickel and samarium tartrate complexes and the MCD of a single crystal of Co/MgO at 12 K and 40.6 kG are reported. Performance of the instrument is comparable to visible‐ultraviolet CD instruments.

ISSN:0034-6748    

DOI:10.1063/1.1685944

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An apparatus and techniques are described which have been found adequate for making nominally 1% accurate specific heat measurements on relatively low thermal conductivity alloys in the range of temperature from 0.5 to 10 K and in magnetic fields of 0 to 1.5 T (15 kG). Emphasis is given to thermometry and to experimental methods of establishing the accuracy of the measurements. Several competing effects which must be quite delicatelybalanced in the design of the calorimeter are discussed and the necessary experimental compromises are described in detail. Some consideration is given to techniques for extending the useful range of temperature and magnetic field.

ISSN:0034-6748    

DOI:10.1063/1.1685945

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An improved type of thin‐film heat gauge has been developed and used to measure heat‐transfer rates from a shock‐heated plasma to the end wall of a shock tube. The gauge is a resistance thermometer consisting of a triplelayered sensor coated by a moderately thick film of SiO2. It was used to measure heat transfer from nonionized argon at temperatures of up to 16 000 K. A marked increase in heat transfer at the onset of ionization near the wall indicates that the gauge can be used to obtain the contribution of free electrons to the thermal transport.

ISSN:0034-6748    

DOI:10.1063/1.1685946

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A simple circuit for cw NMR measurements is discussed. The purpose of this circuit is similar to that of bridge arrangements: The rf at the input of the receiver is compensated by an additional branch within the circuit consisting of a potentiometer and a phase shifter. As shown by theoretical calculations, the sensitivity of the discussed arrangement is higher than similar uncompensated circuits and higher than bridge arrangements as well. The203Tl and205Tl resonances measured with this circuit show signal‐to‐noise ratios comparable to the signal‐to‐noise ratios of the resonances measured with a commercial wide‐line NMR spectrometer.

ISSN:0034-6748    

DOI:10.1063/1.1685947

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A high‐pressure dilatometer was devised to measure the length change of specimens under hydrostatic pressure up to 22 kilobars. The dilatometer uses a linear variable differential transformer and exhibits a hysteresis with pressure cycling. With a careful calibration of the dilatometer vs pressure, instantaneous measurements of the length change of a specimen can be made within a precision of less than 0.025%.

ISSN:0034-6748    

DOI:10.1063/1.1685948

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An automated data collection system has been developed and applied to the measurement of O16/O18ratios with high precision. The design is based on the simultaneous capacitive integration of two ion beams from a mass spectrometer. The results obtained have shown a consistent precision of 10–20 parts per million.

ISSN:0034-6748    

DOI:10.1063/1.1685949

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Pulsed, low temperature, alkali plasmas have been produced by photoionization of the vapor using a xenon flashtube uv source. Results are as follows: for cesium,ne>1011cm−3with 100% ionization; for potassium,ne≈1010cm−3with 2% ionization; and for lithium,ne≈2×1010cm−3. The flashtube spectrum in the 2100–3200 Å range was measured.

ISSN:0034-6748    

DOI:10.1063/1.1685950

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A 0.3–40 &mgr; wavelength‐modulation spectrometer, utilizing dual beam optics and a single detector, has been designed which is free of most of the difficulties present in previously reported instruments. Over the wavelength range of the photomultiplier tube this system, limited by photon noise, is capable of an optical resolution of 6 Å. For purposes of evaluating the performance of the system, the measured derivative spectra of a holmium oxide filter and of a single crystal gallium arsenide plate are reported. Measurements at liquid nitrogen temperatures, in gallium arsenide, produce spectral details that are substantially more pronounced than in electroreflectance or thermoreflectance spectra. The additional resolution permits new optical structures in gallium arsenide to be observed. The values of measured transition energies in this semiconductor confirm many of those earlier reported. New values for the temperature dependence of the band structure are reported.

ISSN:0034-6748    

DOI:10.1063/1.1685951

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An extremely simple, easily used system has been devised for the measurement of the dihedral angle between two plane faces on small specimens. The faces must be specular (rather than diffuse) reflectors, but may be quite lossy. Alignment criteria are extremely loose, but measurement precision is diffraction limited. The system will probably be of most use on objects of submillimeter dimensions

ISSN:0034-6748    

DOI:10.1063/1.1685952

出版商:AIP    

年代:1973

数据来源: AIP