摘要:

This paper describes a dual beam stopped flow apparatus for quantitatively observing rapid (up to 250 sec−1) chemical reactions in turbid suspensions. The unit employs two commercial 150 W xenon arc light sources modulated to produce square light pulses at 5000 cps; two wavelengths of light are selected by monochromators, and the light is delivered to the reaction cuvette of a conventional stopped flow apparatus via a fiber optic light guide ``Y.'' Current and light intensity feedback are utilized to control lamp intensity; simple transistor choppers demodulate the measuring photomultiplier output, and a second photomultiplier is utilized in a differencing scheme to reduce effects of residual lamp instability. The instrument has a limit of detectability of 1×10−3optical density units; crosstalk of signal from one channel into the other channel is 6% of the change being measured. An example of instrument performance is presented; as now constructed, the instrument provides time resolution at least 5 times higher and reagent economy more than 20 times higher than other available dual wavelength spectrophotometers.

ISSN:0034-6748    

DOI:10.1063/1.1720360

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A bomb calorimeter for measuring the heat of detonation of 25 g charges of high explosive is described. A complete calorimetric measurement can be made in 1 h with a precision of 0.3%. Calorimetric measurements and analysis for PETN are described. The data are interpreted with the aid of thermodynamic and hydrodynamic computer calculations. For unconfined or lightly confined charges, the released energy is largely retained in the products which are shocked considerably off the Chapman‐Jouguet isentrope by reflections from the bomb wall. For heavily confined charges, the energy is largely converted to kinetic and internal energy of the confining case, and the essentially unshocked products expand along the Chapman‐Jouguet isentrope. The products of detonation are found to freeze out at 1500 to 1800°K. The heat of detonation of PETN at 298°K is 1490±6 cal/g, H2O(l).

ISSN:0034-6748    

DOI:10.1063/1.1720361

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

Recent results by Crawford and Messel on the development of showers in lead by the Monte Carlo method are used to estimate the energy resolution of total energy absorption scintillation shower counters. It is probable that slight improvements in energy resolution over existing counters can be obtained by using 15 radiation lengths in the direction of the incident particle and sampling the shower after every110radiation length.

ISSN:0034-6748    

DOI:10.1063/1.1720362

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

An ionization gauge for molecular beam work has been developed which uses a field ionization tip as an ion source. Data are given regarding signal‐to‐noise ratio and sensitivity. Means of reducing the rate of tip deterioration are discussed and data given showing moderate reduction in signal strength over a 1 h period. Curves are given showing that the sensitive area of the gauge is small when compared to a 0.25 mm wide molecular beam.

ISSN:0034-6748    

DOI:10.1063/1.1720363

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

Two current sources which give a constant current over a wide range of applied voltage have been built for use in calibrating electrometers having input resistors in the 10+10to 10+12&OHgr; range. The sources consist of sealed parallel plate ionization chambers having one electrode coated with241Am. Calibrations using the rate of charge method spaced over a period of 1 year define the respective current output of the sources as (6.943±0.003)×10−11and (4.263±0.004)×10−12A.

ISSN:0034-6748    

DOI:10.1063/1.1720364

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A naturally occurring, iron rich silicate mineral commonly known as biotite has been found to perform very well as a Brewster angle reflection polarizer in the region 1100 Å to nearly 6000 Å. This observed behavior is somewhat anomalous since it is well‐known that nonabsorbing dielectric surfaces which polarize well in Brewster angle reflection have low reflectivity whereas the light reflected from highly reflecting surfaces has a low polarization. In contrast to this, we have found biotite to have a rather high reflectivity with strong polarization of the reflected light. The characteristics of this polarizer are reported in this paper and the apparent anomaly is resolved in terms of an optical anisotropy hitherto disregarded in this context.

ISSN:0034-6748    

DOI:10.1063/1.1720365

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

An alumina high temperature gas discharge tube with cold windows has been constructed for the investigation of metallic vapor lasers. It offers vacuum tight containment to 1400°C, and flexibility with respect to active material, discharge diameter, type of excitation, and output windows. Pulsed laser oscillations in lead, manganese, and copper have been observed in this apparatus.

ISSN:0034-6748    

DOI:10.1063/1.1720366

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A practical non‐Stark modulated double resonance microwave spectrometer has been constructed and tested in which frequency modulation is applied to one (strong) microwave source, the power from which passes through the sample gas but is prevented from reaching the crystal by filters. The second source does reach the crystal but is unmodulated. The modulation is therefore transmitted to the crystal and tuned amplifier exclusively via the phenomenon of double quantum absorption. The only transitions observed were those which occur as active pairs involving a common energy level, the two frequencies being near the two source frequencies. This provides extremely specific spectra for identification in complex situations, and is a convenient way of searching for linked transitions which are useful for assignment purposes. Because no Stark electrode is needed, it is easier to construct special absorption cells such as coiled guides, high temperature cells, free space paths, etc.

ISSN:0034-6748    

DOI:10.1063/1.1720367

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A gas flow proportional counter designed for use as the detector in a microprobe nondispersive system is described. The counter design incorporates (1) relatively low operating voltage with high multiplication factor, (2) an anode wire support to minimize ``end effects'' on the pulse height distribution curve, and (3) an over‐all design to permit convenient disassembly and replacement of the anode wire or other components. Results of performance studies indicate higher resolving power than similar commercial counters and negligible shift in multiplication factor over a wide range of counting rates.

ISSN:0034-6748    

DOI:10.1063/1.1720368

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A specially designed time‐of‐flight spectrometer has been constructed for studying the ions emitted from an opaque surface in vacuum under bombardment by a Q switched laser beam. Since some of the ions to be studied are emitted with considerable kinetic energy, the spectrometer allows one to make independent measurements of them/eof the ions and of their initial kinetic energies. No other spectrometer design permits simultaneous measurements to be made of these two parameters during the interval of a single laser pulse. The design considerations involved in the construction of this spectrometer are described in some detail.

ISSN:0034-6748    

DOI:10.1063/1.1720369

出版商:AIP    

年代:1966

数据来源: AIP