摘要:

A simple laser interferometer has been utilized to measure the thermal expansion and optical‐length variation with temperature of highly reactive fluorides at high temperatures. The interferometer is a modification of the Jamin interferometer in which a laser beam is split into two parallel beams which traverse nearly identical paths and are reflected from the sample and a reference mirror. The reflected beams recombine to produce an interference pattern. The displacement of the front sample surface, relative to the reference mirror at the back sample surface, allows the thermal expansion to be measured. The sample and reference mirrors are made reflecting by depositing a platinum film on the surface. The same arrangement of beam splitters has been used to measure the variation in optical length with temperature. In this case, the sample is not coated with platinum. Measurements of thermal expansion have been made up to 1000 K above which the platinum film becomes unstable. Optical lengths of various fluorides have been measured up to 1100 K. The platinum is not observed to diffuse into divalent metal fluorides although these samples oxidize readily at certain high temperatures. The advantages and disadvantages of this method are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1137718

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

In order to detect the circular fringes of a Fabry–Perot interferometer with high sensitivity the electronic scanning of an optical multichannel analyzer (OMA) has been modified. Compared to the common scanning Fabry–Perot photomultiplier combination this modification yields a gain in sensitivity of more than a factor of 10. Furthermore, single pulses or strongly fluctuating sources may be measured without the noise problems of a scanning interferometer. The modified OMA is capable of resolving about 90 circles. The system is applied to the detection of the fine structure of weak laser‐excited phosphorescence spectra.

ISSN:0034-6748    

DOI:10.1063/1.1137719

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A technique which displays the fractional order of optical interference by the azimuthal angle of radial arm has been improved by using a digital electronic circuit such as phase‐locked loop and D flip–flop. The phase quadrature reference signals of this system are derived by reforming a reference signal and shifting it by a quarter wavelength referring to its waveform. As the result the orthogonal phase relation of the two signals is not affected by the frequency of the signal. This system has been proven to operate properly over the frequency range of 200–600 kHz without readjusting the electric system.

ISSN:0034-6748    

DOI:10.1063/1.1137720

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A single‐mode fiber‐optic interferometer for measuring subangstrom vibrations has been designed and constructed. The interferometer is based on the Fizeau configuration and employs peak detection schemes in the signal processing. The instrument has been used to measure the displacement of a cricket’s tympanic membrane.

ISSN:0034-6748    

DOI:10.1063/1.1137721

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The design and performance of a discharge‐excited N2laser which emits 7‐ns‐long pulses of 337.1‐nm wavelength at a 300‐Hz repetition rate is described. The peak power is 150 kW at 50 pps and the shot‐to‐shot amplitude stability is ±1.5%. The construction compromises between requirements of high power, high repetition rate, and good stability.

ISSN:0034-6748    

DOI:10.1063/1.1137722

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A new technique for the measurement of Raman spectra of small particles in suspension, such as biological cells, is described. The particles flow through a rectangular glass capillary mounted at the sample position of a laser Raman microspectrometer. The measuring volume inside the glass capillary is comparable to the volume of the particles. The elastic forward light scattering of the laser beam by the particles is used to monitor the presence of a particle in the measuring volume. Photon pulses from the Raman detector are counted only when a particle is inside the measuring volume. In this way the background signal caused by the suspending medium is suppressed, thus allowing measurement at very low particle concentrations. The technique, which is called gated Raman spectroscopy (GRAS) combines features such as: efficient light collection, suppression of background, and the possibility to use high laser powers. A great advantage is that this technique can be used for the study of (living) biological cells under physiological conditions. The GRAS technique is demonstrated with polystyrene particles and with unicellular algaechlorellavulgaris.

ISSN:0034-6748    

DOI:10.1063/1.1137723

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The construction and operation of a high‐sensitivity photoelectron spectrometer, specifically designed for studying reactive transient species, is described. Fast data acquisition is used to minimize spectral drift problems caused by contamination resulting from species production conditions. The spectrometer is equipped with sample differential pumping to retard contamination of the electron optics and its modular design enables individual components to be readily dismantled for cleaning purposes. A microchannel‐plate (MCP)/phosphor/silicon‐intensified‐target (SIT) camera detector is used, operated under modest voltage conditions. A unique, dedicated, dual‐buffer, data interface is constructed, incorporating the use of a video window to select data. The interface can be used in a stand‐alone mode for rapid data examination, when optimum spectrometer conditions can conveniently be established using the detector two‐dimensional imaging capability and a standard TV monitor for assessment of line image quality. Preliminary results show reductions in data‐acquisition times of up to 75 compared to equivalent single‐channel detector experiments. Several studies of transient species have been performed, which had proved unsuccessful on earlier generation spectrometers.

ISSN:0034-6748    

DOI:10.1063/1.1137724

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A new high‐resolution, differentially pumped, electron energy‐loss spectrometer with the capability of measuring both valence and inner‐shell spectra (at impact energies of 1–10 keV) has been constructed. Advanced electron optics have been incorporated, and the design and operation of the electron optics is discussed. Spectra of N2are presented, demonstrating the significant improvements obtained in signal to noise and collection time in the inner‐shell region compared with previous instrumentation. In addition, both valence and inner‐shell spectra of HCl are presented, demonstrating the efficiency of the differential pumping, and the ability of the instrument to study highly reactive target species.

ISSN:0034-6748    

DOI:10.1063/1.1137713

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A low‐power diffractometer with a microfocus x‐ray tube with the focus on its window is described. X‐ray paths are kept short and the whole of the diffracted cone enters the detector, which leads to an improved sensitivity as compared to conventional instruments. For the most intense quartz line, sensitivities of 920 counts per second per microgram have been obtained at a tube power of 1.25 W and Cr radiation. Specimens of less than 50‐ng quartz can be detected. The low power results in low weight, less than 20 kg, thus allowing the instrument to be portable.

ISSN:0034-6748    

DOI:10.1063/1.1137714

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A titration vessel with a built‐in closed‐loop flow system connected to a flow‐through spectrophotometric absorption cell has been designed and tested. No pump is necessary; the flow is actuated when the solution is stirred.

ISSN:0034-6748    

DOI:10.1063/1.1137715

出版商:AIP    

年代:1984

数据来源: AIP