摘要:

A simple CO2waveguide laser with fixed alignment is described and the operating characteristics for various gas mixtures given. Maximum power obtained was 3 W at a working pressure of 120 Torr. Alignment was still maintained after three years of operation. With a fresh filling of gas, power at the 1‐W level was routinely obtained over a day’s running time.

ISSN:0034-6748    

DOI:10.1063/1.1137536

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A vernier fringe‐counting circuit designed for use with a Kowalski‐type wavemeter is described. Wavelength measurements made with this device have a high reproducibility of 5×10−9(or 1/50 of a fringe) and measured accuracy of 4×10−9. The results of accuracy tests are presented along with systematic errors incurred when the wavelengths of two He–Ne lasers (632.9 nm) are compared by the vernier method.

ISSN:0034-6748    

DOI:10.1063/1.1137537

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A simple liquid‐nitrogen Dewar has been constructed to hold semiconductor platelets for use in a ring laser assembly. Laser action in an external ring cavity is observed when the platelets are longitudinally pumped by an Ar+laser. Microscope objectives mounted outside the Dewar are used to focus the pump beam as well as the lasing beam onto the crystal. Positioning of the platelets in horizontal and vertical directions is accomplished by attaching the Dewar to anxyzstage.

ISSN:0034-6748    

DOI:10.1063/1.1137538

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Monitoring the optical pulses from mode‐locked and synchronously pumped continuous wave (cw) lasers, reference beams are taken from the main beams with beam splitters. Depending on the angle with respect to the incident beam and the direction of the rotation axis of the beam splitter, light fractions of different polarizations can be selected. Based on practical and theoretical considerations an alternative beam‐splitter mount has been designed which efficiently utilizes the available optical power.

ISSN:0034-6748    

DOI:10.1063/1.1137539

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The performance characteristics of the Hamamatsu R928 side‐window photomultiplier tube have been evaluated in the picosecond time domain. This phototube is proposed as an attractive solution to the problem of high time resolution when a sync‐pumped dye laser is combined with the single‐photon time correlation method for determining fluorescence lifetimes and measuring time‐resolved emission spectra and polarization anisotropy. It combines excellent timing characteristics in the single‐photon mode and a small‐to‐negligible wavelength effect with high gain, low noise, and low cost. Twice the resolution previously reported has been obtained.

ISSN:0034-6748    

DOI:10.1063/1.1137540

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

An acoustic wave technique is described which provides an absolute calibration of the amplitude of the light scattered from a CO2laser beam at near‐forward angles by fluctuations in plasmas or other media. This technique also provides a direct measure of the wavelengths of fluctuations that can be resolved by CO2laser light scattering. Using simple vibrating membranes, acoustic waves with wavelengths from a few millimeters to several centimeters can be generated with accurately measured amplitudes. Laser scattering from these waves verifies that wavelengths as long as 2 cm can be resolved with small‐angle CO2laser scattering. For the case of heterodyne detection, calibration of the scattered wave amplitudes is obtained to within ± 20%.

ISSN:0034-6748    

DOI:10.1063/1.1137541

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Reducing the front face echo is one of the major problems encountered in backscattering measurements of optical fibers. A simple method is proposed in order to eliminate completely this unwanted signal for both multimode and single‐mode fibers. The setup is very simple and no special preparation of the fiber is needed. The insertion losses of the filtering device are very low and the detector is protected against direct reflections. In the case of multimode fibers a selective analysis of the backscattered signal can be performed.

ISSN:0034-6748    

DOI:10.1063/1.1137542

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

This paper describes an improved differential photocurrent method of measurement of optical‐absorption coefficient &agr; and minority‐carrier diffusion lengthL. A prototype instrument can detect signals of the photocurrentIp, the differential photocurrent &Dgr;Ip, and the depletion‐layer widthWof sample diode, and plot automatically two linear relationships: log(&Dgr;Ip/ &Dgr;W) vsWandIpvs &Dgr;Ip/ &Dgr;W. From these plots, &agr; andLare readily obtained. Performance of the instrument is demonstrated using a Au–GaAs 0.62P0.38Schottky‐barrier photodiode.

ISSN:0034-6748    

DOI:10.1063/1.1137543

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The principle and experimental setup of time‐resolved photoelectron spectroscopy are outlined. In comparison to conventional molecular beam relaxation spectrometry a reaction channel is analyzed not only at the end but prior to the end. In at least three points time‐resolved photoelectron spectroscopy is superior to photoelectron spectroscopic experiments under static and direct current adsorption conditions: (1) a general increase in detection power of transient adsorbates and contaminations; (2) the possibility to discriminate by individual relaxation time between species that cannot be resolved in their binding energy; and (3) a significant simplification of the mathematical formalism in comparison to conventional molecular beam relaxation spectrometry and a more straightforward understanding of the results, in particular the chemical identification of transient species. This is illustrated with time‐resolved UV‐photoelectron spectra of intermediate adsorbed carbon in the catalytic decomposition of methanol on iron and with time‐resolved x‐ray photoelectron spectra of intermediate adsorbed oxygen in adsorption and catalysis of methanol/oxygen mixtures on iron.

ISSN:0034-6748    

DOI:10.1063/1.1137544

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

An adiabatic calorimeter for the simultaneous measurement of enthalpies of vaporization and vapor pressures of certain coal chemicals is described. The calorimeter was tested using benzene for which accurate experimental data exists in the literature. Benzene is one of the substances recommended by IUPAC as a reference substance for calorimetric studies. The uncertainty in the benzene data is ±5 J/mole in the temperature range of 350 K (very close to the boiling point) to 480 K (around 0.85 times the critical temperature). Both vapor pressure and enthalpies of vaporization of benzene showed excellent agreement with the available literature data.

ISSN:0034-6748    

DOI:10.1063/1.1137545

出版商:AIP    

年代:1983

数据来源: AIP