摘要:

This work is concerned with the analysis of the signals which can be recovered in a phase-sensitive detector after either transmission through or reflection from a Fabry–Perot interferometer of a phase-modulated light. The frequency responses are obtained and compared, the effects of amplitude modulation which result in offsets and line shape distortions are analyzed, the conditions to reduce the in-loop frequency noise are examined taking into account the electronic noise, when the source is locked to the cavity by means of a high gain control system. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148079

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An analytical expression and a perturbation formula for the cavity resonant frequency dependence of plasma are derived for the cylindricalTM010-microwave plasma cavity. A comparison between the exact and the approximate solution shows that the perturbation theory can be used accurately to analyze the perturbation effect on the cavity resonant frequency caused by microwave plasma in low pressure microwave excited gas lasers. A new method is proposed to prevent detuning of the cavity by the perturbation of the plasma and glass tube, so that a uniform and steady-state microwave plasma is successfully formed and a stable laser output power is also obtained. The electron density and the microwave dielectric constant of a tube shell can be measured by the perturbation approach. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148080

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A W/Si multilayer was used to determine the degree of circular polarization of the soft x-ray radiation of the European Synchrotron Radiation Facility helical undulator HELIOS I. The multilayer, manufactured by vapor deposition serves as a wideband tunable polarization analyzer in the photon energy range from 520 to 930 eV. The characterization of the multilayer’s analyzing power, varying from 0.82 to 0.25 for these energies, indicates that it operates close to its calculated specifications. The lack of phase-shifters applicable in this energy range was overcome by a detailed analysis of the unpolarized background identified as radiation from the magnetic lattice. In this way, the degree of circular polarization of HELIOS I was determined to exceed 0.85 forh&ngr;>685 eV.©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148081

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

At the Advanced Light Source an undulator beamline, with an energy range from 6 to 30 eV, has been constructed for chemical dynamics experiments. The higher harmonics of the undulator are suppressed by a novel, windowless gas filter. In one branchline high-flux, 2&percent; bandwidth radiation is directed toward an end station for photodissociation and crossed molecular-beam experiments. A photon flux of1016 photon/shas been measured at this end station. In a second branchline a 6.65 m off-plane Eagle monochromator delivers narrow bandwidth radiation to an end station for photoionoization studies. At this second end station a peak flux of3×1011was observed for 25 000 resolving power. This monochromator has achieved a resolving power of 70 000 using a 4800 grooves/mm grating, one of the highest resolving powers obtained by a vacuum ultraviolet monochromator. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148082

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A fiber optic frequency shifter capable of shifting the frequency of light traveling through the fiber has been designed, constructed, and tested. The frequency of the transmitted light is shifted by stretching and contracting the optical fiber that is wound around two piezoelectric ceramic tubes. The frequency of the light is shifted by linearly changing the path length along which the light must travel. The diameters of two piezoelectric ceramic tubes are changed when a linearly increasing electric field is applied to the tubes. A servo control system is used to correct and compensate for nonlinearity of the piezoelectric material and assembly. A frequency shift of up to 305 Hz for up to 2.5 s with a linewidth of less than 1 Hz is achieved with the present setup. This frequency shifter has been successfully applied to a laser light scattering apparatus for which heterodyne experiments are made for particle electrophoretic mobility and zeta potential measurements. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148083

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We describe the design and performance of a new high-speed imaging spectrometer system developed for the spectral analysis of micrometer-sized features in transmitted light. The instrument utilizes the wavelength range from ultraviolet (UV) to near infrared (NIR) (250–975 nm). The extension into the ultraviolet range is to our knowledge unique. The system comprises two white light sources (xenon and halogen lamps), a motorized sample stage, microscope optics with slit-determined field of view, and three (UV, visible and NIR) parallel optical recording channels. The dispersive optical recording system is based on holographic gratings and uses charge-coupled-device (CCD) cameras as imaging detectors. The instrument has been fully integrated with data acquisition and control systems. Subsequent data analysis is performed by dedicated software. The instrument provides spectral images from narrow wavelength bands (5 nm). In such an image the spectral information from a selected wavelength band is depicted with its corresponding geometric location, i.e., a single pixel on the CCD chip. Hence, objects can be visualized in different wavelength bands and a spectrum can easily be produced for each location of the object. The instrument can measure objects up to900 &mgr;m×27 mmwith a spectral resolution better than 5 nm and a spatial resolution better than 5 &mgr;m. The imaging spectrometer system provides a powerful combination of spectroscopy and image processing for use in many applications in research, control and quality assessment, where spectral information and its location are of interest. Although the system has been primarily developed for applications in the pulp and paper industry, it has a vast potential for spectroscopic analysis with a micrometer spatial resolution in general and for measurements of impurities and their locations in products in particular. As an example of a measurement, spectral image data from a wood fiber are presented. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148111

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have designed, built, and tested a total-electron-yield detector for the collection of x-ray absorption spectra. The virtues of this detector are its compact size and simplicity of design, fabrication, assembly, and use. Sample exchange and realignment with respect to the incident beam are easily performed. The design and performance of this detector are presented and discussed in comparison with other detection schemes.

ISSN:0034-6748    

DOI:10.1063/1.1148084

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A compact ultrahigh vacuum (UHV) x-ray diffractometer was designed and constructed using a small rotating-anode x-ray source of 18 kW. Its UHV specimen chamber is 200 mm high and 140 mm in diameter and can be evacuated up to3×10−8 Pa.The x ray is incident into the chamber through a thin Be window, 0.2 mm thick and 30 mm in diameter. Diffracted and scattered x rays are taken out through another Be window, 0.4 mm thick and 60 mm in diameter. All the equipment, a rotating-anode x-ray source, an incident monochromator, and a two-circle diffractometer onto which an UHV specimen chamber and a conventional scintillation counter are mounted, are arranged on only one optical table, 70 cm wide and 90 cm in length. Configuration of the specimen holder in the chamber, which is designed for the surface glancing angle scatterings at present, can be controlled from outside of the vacuum. The apparatus is the best suited toin situobservations of growing crystal surfaces during the deposition. A preliminary experiment of the glancing angle scattering of mechanically polished silver polycrystal surfaces gave an order of103counts−1of scattered x-ray intensity at its specular reflection angle, which is enough to derive a significant interpretation of the surface structure. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148085

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Conventional zero-field optically detected magnetic resonance (ODMR) is normally performed by using a slow-wave helix for microwave excitation with a quality factor Q≈1. With available microwave sources this low Q factor leads to long microwave pulse lengths for coherent pulse experiments(&pgr;-pulse duration of about 300 ns for 20 W microwave excitation power). For our zero-field experiments we took advantage of the bridged loop-gap microwave resonator configuration with relatively high Q factor. Without the possibility of tuning the Zeeman energy level splitting as in electron paramagnetic resonance (EPR), in zero-field ODMR the resonator has to cover a wide range of frequencies. We are able to tune our probehead in the range of 1.9–8 GHz with a loaded Q factor of up to 800 by using interchangeable bridged loop-gap resonators of various designs. Thereby, the pulse lengths, compared to the slow-wave helix, could be reduced by nearly one order of magnitude(tresonator&pgr;=45ns employing the same microwave power of 20 W). Experimental data are presented for triplet states of photoexcited acridine and benzophenone molecules at different resonance frequencies for their|Tx⟩−|Tz⟩transitions(&ngr;=2.472GHz and&ngr;=5.226GHz), respectively. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148086

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We describe an experimental setup for the investigation of the chemical reactivity of size-selected, supported clusters. The clusters are generated by a high frequency laser vaporization source. After mass selection and energy control the clusters are deposited under ultrahigh-vacuum conditions and with low kinetic energy onto thin oxide films grown on metal single crystals. Such films are ideal in their function as supports for size-selected deposited metal clusters. Measured currents of mass-selected niobium cluster ions were of the order of 1 nA and are high enough for fast deposition rates. Adsorbed molecules used on the one hand as probes to characterize the supported clusters and on the other hand for studying chemical reactions on these clusters are investigatedin situby Fourier transform infrared spectroscopy, temperature desorption spectroscopy, and Auger electron spectroscopy. The performance of these analytical tools is illustrated with CO adsorbed on Ni atoms supported on thin MgO(100) films grown on a Mo(100) single crystal. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148113

出版商:AIP    

年代:1997

数据来源: AIP