摘要:

A multiple‐frequency heterodyne radiometer is proposed for the detection of radiation from known species moving with unknown velocities. Expressions for the signal‐to‐noise ratio and the minimum detectable total power are obtained for sinusoidal signals and for Gaussian signals with both Gaussian and Lorentzian spectra. In distinction to the conventional system, knowledge of absolute line rest frequencies and a stable, tunable local oscillator are not required. The system may find use in the detection of certain remote species such as interstellar molecules and pollutants. A number of potential applications are examined.

ISSN:0034-6748    

DOI:10.1063/1.1134023

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A Drickamer‐type apparatus has been made in which the highly‐stressed tip regions of the Carboloy pistons are of dense sintered diamond. Experiments indicate that this apparatus is capable of attaining static pressures of over 400 kilobar on a newly revised scale. The results show that the 1970 revised pressure scale of Drickamer needs further revision downwards for the range above about 150 kilobar. A pressure scale based on electric resistance transitions up to 400 kilobar is proposed. Resistance vs press force curves are shown for Bi, Fe20Co, Fe40Co, CdS, GaP, BP, NaCl, and graphite.

ISSN:0034-6748    

DOI:10.1063/1.1134031

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Electron spectrometers working with electrostatic deflection are characterized by a typical background structure. Experimental investigations and model calculations for a 127° analyzer show that the major part of this background is caused by specular reflections of the electrons from the deflection plates towards the exit slits. The background is reduced by a factor ≳10 when the deflection plates are appropriately corrugated. In a comparison with the most rational general CFF available, that of Ermer and Lifson, the most significant discrepancies found to occur are those for certain stretch–bend couplingsassumedto be zero in the CFF, but shown to be appreciable by quantum calculation. It is observed that these couplings, but not the stretch–stretch couplings, are well accounted for by a steric interaction model. Theabinitiocubic constants examined display the same pattern of conformity with a steric model. Bend–bend–bend and bend–bend–stretch but not all stretch–stretch–stretch interactions agree with those of the steric model. The partial success of the steric model shows that it is possible to represent a large number of interaction constants, quadratic and higher order, by a small number of parameters in molecular mechanics. The failure of the steric model to account for predominantly stretching interactions confirms that ’’classical’’ nonbonded interactions as embodied in conventional Urey–Bradley fields are not the only major contributors to off‐diagonal force constants. An alternative model, the anharmonic model of Warshel, as augmented by Kirtmanetal., was found to account well for pure stretches but not for bends or stretch–bend interactions.

ISSN:0034-6748    

DOI:10.1063/1.1134064

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

An optical system is described having three equal paths split from a single beam and recombined into a single beam. A method for electronically processing the signal to obtain the transmittance and reflectance as well as an interfacing system, which allows complete programming of scans and direct data processing, is also described. The results of simultaneous measurements of transmittance and reflectance of amorphous As2S3and the reflectance squared of crystalline germanium are presented in which a relative precision better than 1×10−4was achieved. Also mentioned are various applications, such as differential reflectance and measurements with incandescent samples.

ISSN:0034-6748    

DOI:10.1063/1.1134065

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A method is described for the selection of a mode‐locked pulse from a laser by the use of a laser‐initiated krytron‐switched Blumlein structure that replaces the usual high voltage spark gap. The main features are an all electronic circuit coupled to a longitudinal mode KD*P Pockels cell that has a fast risetime and high extinction ratio. The result is an inexpensive, noise‐free pulse selector that provides a stable source of switched out pulses.

ISSN:0034-6748    

DOI:10.1063/1.1134066

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A sample cell and optical mount for use in laser Raman spectroscopic studies of adsorbed species at elevated temperatures is described.InsituRaman spectra of pyridine adsorbed on 60–120 mesh silica gel at room temperature, 75 °C, and 150 °C are reported. The cell has also been used in studies of other species adsorbed on silica, alumina, and platinum wire.

ISSN:0034-6748    

DOI:10.1063/1.1134067

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

This paper describes an improved method and apparatuses based on it for the measurement of the dielectric constant and the dissipation factor at very high frequencies. This method is a combination of the Hartshorn and Ward, Lynch, and liquid immersion methods. The direct purpose is to measure low‐loss polyethylene which is to be used in submarine telephone cables at 36 and 100 MHz in Japan. By using a 0.5∼2.0 mm thick disk specimen, the dielectric constant can be measured to an accuracy of 0.3%, the dissipation factor to several &mgr;rad, and the mean thickness to several &mgr; without any kind of correction. The three equations for them are simple and independent of the frequency. This method is easy to use and takes little time, for the values to be measured for each specimen are only three in a series of measurements, and the mechanical thickness measurements are not required.

ISSN:0034-6748    

DOI:10.1063/1.1134068

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A simple modification to a conventional single coil pulsed NMR spectrometer is described which damps the final stage of the transmitter at low rf levels. For an unmodified Bruker SXP spectrometer a receiver recovery time of 7.7 &mgr;sec is obtained at 60 MHz; this time improves to 5.5 &mgr;sec on adding the ’’low level damper.’’

ISSN:0034-6748    

DOI:10.1063/1.1134069

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A spectrophotometer has been adapted for use as a simultaneous observation–exposure system for irradiation of biochemical samples by 1.7–2.6 GHz electromagnetic radiation. A waveguide applicator is mounted vertically in the sample compartment of a Cary 15 spectrophotometer such that the sample can be placed simultaneously in the light path and in a slot in the applicator. A standard 1‐cm path square cell contains the sample which is irradiated through the open top of the cuvette. Temperature of the sample and an unirradiated reference are monitored continuously without measurable interference from the microwave field. Temperature can be controlled within a few tenths of a degree between 15 ° and 40 °C, and an absorbed dose rate can be calculated using thermal measurement techniques. Microwave generator output and reflected power are monitored at all times. The frequency can be changed easily and standing waves minimized by adjusting a waveguide tuning section. The microwave energy within the basic frequency range can be applied as continuous wave or modulated. The quality of the absorption spectra is not measurably impaired, and the flexibility of the spectrophotometric technique remains intact.

ISSN:0034-6748    

DOI:10.1063/1.1134070

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

This article presents a design for a simple, inexpensive magnetic recirculating pump. It consists of a piston and cylinder with a separate check valve which can be either normally open or normally closed. The interior offers minimal surface area for adsorption and, with proper dimensioning and material selection, the pump can operate over wide pressure and temperature ranges. A prototype model with cylinder dimensions 22.2 mm o.d.×15.9 mm i.d. ×6.35 cm circulates at 26 cm3/sec (10 cm of H2O differential pressure). The dimensions of the prototype allow an operable pressure range of 0⩽P⩽703 kg cm−2at room temperature. The temperature range is 100⩽T⩽500 K.

ISSN:0034-6748    

DOI:10.1063/1.1134071

出版商:AIP    

年代:1975

数据来源: AIP