摘要:

An instrument is described which measures small differences in optical reflectivity or transmissivity of two specimens. The apparatus has been used to investigate surface effects such as corrosion or deformation of thin surface layers as well as metallurgical transformations or compositional modulation. A complete ``differential spectrogram'', i.e., scan through the visible and near uv region, is performed in less than 1 min.

ISSN:0034-6748    

DOI:10.1063/1.1686156

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An electronic correlator is described in which the arrival times of photoelectric pulses are registered directly in digital form. Pairs of interval times, corresponding to three photoelectric pulses, are then mapped onto a one‐dimensional array of numbers, and are stored in the memory of a multichannel analyzer. The stored set of numbers provides a two‐dimensional histogram, that is a measure of the third order intensity correlation function. This technique allows information to be accumulated at a higher rate than with time‐to‐amplitude converters.

ISSN:0034-6748    

DOI:10.1063/1.1686157

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

In the energy meter described here the CO2laser radiation is almost completely absorbed by an Al2O3surface on an aluminum plate. The high absorption of the surface (≥95%) eliminates the need for calibration and the laser energy is computed by measuring the temperature rise of a plate with known thermal capacity. Experimentally we find that the calorimeter noise level corresponds to an energy density of about 2 mJ/cm2. Calculations indicate that the instrument is capable of measuring the energy of a single pulse that is 1 nsec wide, provided the pulse contains an average energy density of 10 mJ/cm2. We have estimated the radiation and convection losses and found them to be negligible. The calorimeter is good for radiation between 8.5 and 11 &mgr;; however, with modifications the bandwidth could easily be increased.

ISSN:0034-6748    

DOI:10.1063/1.1686158

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A 50‐&mgr; glass filament from a fiber‐optics bundle, bent at 90° near the lower end and fastened to an adjustable support, proves to be a better light pickup than the usual pinhole aperture for high‐resolution scanning of a laser beam. Scans of a 50‐mW laser beam were used to develop a spatial filter combined with a short‐focus collimating lens which yields a uniform, Gaussian‐shaped beam with no increase in size.

ISSN:0034-6748    

DOI:10.1063/1.1686159

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A continuous wave ultrasonic interferometer is described which makes possible measurement of both absolute values of and small changes in the elastic constants of solids using commercially available subsystems.

ISSN:0034-6748    

DOI:10.1063/1.1686160

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An isothermal titration microcalorimeter having a volume of 4 ml and capable of temperature control to ± 2 × 10−5°C is described. Major components include a constant temperature water bath controlled to ± 3 × 10−4°C, a platinum reaction vessel, and an isothermal control circuit consisting of constant Peltier thermoelectric cooling and variable Joule heating controlled by a thermistor in an ac Wheatstone bridge circuit. The calorimeter was tested by measuring the heat of ionization of water and was found to produce data accurate to ±0.1% for this system. The instrument is ideally suited for measuring heats where small samples are used such as in the investigation of many biological systems.

ISSN:0034-6748    

DOI:10.1063/1.1686161

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The description and use of a precision goniometer polishing jig are presented. Specimens pre‐oriented within 6° can be exactly oriented and prepared on the jig. Samples of single crystals of refractory metals have been prepared with a surface polished within 1/20 of a wavelength of sodium light and with an orientation to within 15′ of the desired plane. This jig can operate on any horizontal running polishing machine.

ISSN:0034-6748    

DOI:10.1063/1.1686162

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A simple secondary ion mass spectrometry (SIMS) apparatus has been constructed. A Superior Electronics, 3K/5U, electron gun has been converted to an ion gun capable of producing a 1 mm diam, 2 keV, 1 &mgr;A beam. To achieve wide dynamic range at high resolution in the mass analysis of the secondary ions using a quadrupole mass spectrometer (QMS), the ion injection energy must be ≲4 eV. Ions sputtered from the target with these low energies are selected with a simple cylindrical mirror analyzer placed in front of the QMS. Single monolayers are easily analyzed using a beam density of 10−7A/cm2; bulk profile analysis is performed while sputtering with higher beam densities. Signal‐to‐background ratios in excess of 106are acheved. Positive SIMS of clean and cesiated GaAs single crystals have been obtained and are discussed. A composition versus depth profile of a GaAs&sngbnd;AlxGa1−xAs sandwich structure is also presented.

ISSN:0034-6748    

DOI:10.1063/1.1686163

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Modifications of commercial equipment for high temperature thermal analysis are described. Physical changes allow the use of silica or alumina as encapsulating materials in addition to the normal metallic sample holders, while electronic modifications facilitate instrument use to study small thermal effects at temperatures in the range 1000–1500°C. A method for encapsulating samples in alumina tubes is also described.

ISSN:0034-6748    

DOI:10.1063/1.1686164

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An apparatus is described which automatically records the times at which the resistance of a system undergoing change becomes equal to a series of fixed resistors of known values. The apparatus consists of an ac conductance bridge coupled to a null detector which triggers a stepping switch and a digital clock. This arrangement is particularly suitable for measuring the rates of chemical reactions in solution.

ISSN:0034-6748    

DOI:10.1063/1.1686165

出版商:AIP    

年代:1973

数据来源: AIP