摘要:

This article presents a review of techniques and instrumentation for using x rays and synchrotron radiation in high-pressure experiments. The review focuses on x-ray diffraction experiments using diamond anvil cells. After a brief introductory passage, details about diamond anvil cells, large volume apparatus, pressure measurement, and simultaneous high-temperature and high-pressure instrumentation are provided, with adequate references to these topics. A section on adapting x-ray methods for use with high-pressure apparatus lists the problems encountered. Examples of studies are presented using energy dispersive diffraction, angle dispersive diffraction, infrared spectroscopy, x-ray absorption spectroscopy, and single-crystal techniques. The current trend indicates that energy dispersive diffraction, so far the mainstay of high-pressure powder diffraction with synchrotron sources, has lost some ground to angle dispersive diffraction, due to advances in instrumentation in the latter method. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147969

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A simple interferometer for matching the wavelengths of tunable lasers is described. Our interferometer uses the angular dispersion of a diffraction grating at the Littrow angle to produce a tilted wavefront with respect to a reference mirror in an opposing arm of a Michelson interferometer. As a first step, the resulting interference pattern is adjusted to produce a null fringe using a reference laser as a wavelength standard. When a tunable laser, such as a laser diode, is used to illuminate the system, the laser is simply tuned to reproduce the null fringe pattern established using the reference laser. When so tuned, the wavelength of the tunable laser is matched to that of the reference laser within about 3 GHz, close enough for optical heterodyning.

ISSN:0034-6748    

DOI:10.1063/1.1147971

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The thermal stationary nonlinear refraction is determined with enhanced sensitivity by measuring the profile distortions of a cw probe light beam in the presence of absorption of a collinearly propagating pump light beam. By measuring the total profile distortion of the probe beam for different position of the sample cell, a signal similar to the well-knownZ-scan signal is obtained. Using the Gaussian decomposition method a simple formula is deduced which relates the induced thermal phase shift to the magnitude of the observed signal. Phase shifts as low as &lgr;/40000 with a signal-to-noise ratio of unity becomes detectable with this technique. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147972

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A photon detector with spatial and temporal resolution capabilities is described. The detector consists of an image intensifier and a position-sensitive photomultiplier tube. It has2.5×103resolvable pixels, a dark count rate of5×10−2pixel−1 s−1, and a quantum efficiency of 12&percent; at 670 nm. The maximum data rate for a pixel is 500 kHz, which is also the limit of the entire detector aperture. The absolute time of a single event can be determined to within 100 ns. The single pixel response was found to be linear with incident intensity for short pulses of light containing up to several thousand photons. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147973

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Imaging characteristics of channel plate x-ray collimators have been investigated in the low energy range for applications of two-dimensional x-ray spectrometer. Improvement of the degradation of spatial resolution due to x-ray reflection inside a hollow channel has been considered by utilizing a focusing action of the channel plate collimator. Spatial extent of images through the channel plate collimator have been measured systematically by using a low energy point x-ray source and have been compared with results of ray-tracing calculations. It is shown that the spatial extent of the image consisting of the focusing component is limited by the geometrical divergence of the channel plate collimator. The possibility of two-dimensional imaging spectroscopy as well as the focusing action is discussed. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147974

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A tunable diode laser spectrometer modified for the investigation of molecular gases and van der Waals complexes in a supersonic jet is described. Simply constructed, reliable pulsed sources with15 &mgr;m×(7–40 mm)slits were used at a repetition rate of the order of 100 Hz for the cooling of gases and for the formation of complexes. A double modulation technique based on a simultaneous modulation of the jet and a 10 kHz wavelength modulation of the diode laser enabled measurements of absorbances1.3×10−5(3×10−5in relative absorption) at operating conditions corresponding to 1 s output time constant of the registration system. White type multireflection optics enlarged the absorption path of the laser radiation through the jet by 16 times. New spectra of the van der Waals complexesAr–CH4andKr–CH4in the7 &mgr;mregion are presented in order to show the characteristics of the spectrometer. The final resolution in the recorded spectra was better than 40 MHz. The rotational temperature of the complexes produced by the present jet source was 7–10 K, which could be compared to the 13 K excitation temperature measured for the two lowest rotational states ofFsymmetry of the methane monomer. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147975

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A new fast scan submillimeter spectroscopic technique (FASSST) has been developed which uses a voltage tunable backward wave oscillator (BWO) as a primary source of radiation, but which uses fast scan(∼105Doppler limited resolution elements/s) and optical calibration methods rather than the more traditional phase or frequency lock techniques. Among its attributes are (1) absolute frequency calibration to∼1/10of a Doppler limited gaseous absorption linewidth(<0.1 MHz, 0.000 003 cm−1), (2) high sensitivity, and (3) the ability to measure many thousands of lines/s. Key elements which make this system possible include the excellent short term spectral purity of the broadly(∼100 GHz)tunable BWO; a very low noise, rapidly scannable high voltage power supply; fast data acquisition; and software capable of automated calibration and spectral line measurement. In addition to the unique spectroscopic power of the FASSST system, its implementation is simple enough that it has the prospect of impacting a wide range of scientific problems. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147970

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A new instrument employing molecular beam techniques and laser induced fluorescence (LIF) for measuring the reactivity of gas phase radicals at the surface of a depositing film has been designed and characterized. The instrument uses an inductively coupled plasma source to create a molecular beam containing essentially all plasma species. A tunable excimer pumped dye laser is used to excite a single species in this complex molecular beam. LIF signals are imaged onto a gated, intensified charge coupled device (ICCD) to provide spatial resolution. ICCD images depict the fluorescence from molecules both in the molecular beam and scattering from the surface of a depositing film. Data collected with and without a substrate in the path of the molecular beam provide information about the surface reactivity of the species of interest. Here, we report the first measurements using the third generation imaging of radicals interacting with surfaces apparatus. We have measured the surface reactivity of SiH molecules formed in a 100&percent;SiH4plasma during deposition of an amorphous hydrogenated silicon film. On a 300 K Si (100) substrate, the reactivity of SiH is near unity. The substrate temperature dependence (300–673 K) of the reactivity is also reported. In addition, reactivity measurements for OH molecules formed in a water plasma are presented. In contrast to the SiH molecule, the reactivity of OH radicals is 0.55±0.05 on the surface of a Si (100) substrate. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147976

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have demonstrated a resolution of 0.8 meV [full width at half-maximum (FWHM)] for threshold photoelectron measurements using a steradiancy-type zero kinetic energy photoelectron (ZEKE-PE) analyzer and the high resolution monochromatized vacuum ultraviolet (VUV) undulator synchrotron radiation of the chemical dynamics beamline at the advanced light source (ALS). Using this high resolution ZEKE-PE energy analyzer to filter prompt electrons and by employing a proper voltage pulsing scheme adapted to the timing structure of the ALS, we have achieved a resolution of 0.5 meV (FWHM) for pulsed field ionization photoelectron (PFI-PE) measurements with little contamination from prompt photoelectrons produced from direct photoionization and autoionizing processes. The experiment scheme presented here is generally applicable to PFI-PE studies using multi-bunch VUV synchrotron radiation at other synchrotron radiation facilities. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147977

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Energy-selected electron-ion coincidence spectroscopy for the study of surface dynamics combined with synchrotron radiation (SR) was developed. The equipment consists of an electron gun, a cylindrical mirror analyzer (CMA), and a time-of-flight (TOF) ion mass spectrometer. A sample surface was excited by SR, and energy of the emitted electron was analyzed by the CMA. The TOF spectrum of the desorbed ions was measured taking the energy-analyzed electron signal as the starting trigger. The ions coincidently desorbed with the electron gave a characteristic peak in the TOF spectrum. The apparatus was evaluated on the basis of photoelectron–photoion coincidence (PEPICO) and Auger electron–photoion coincidence (AEPICO) measurements ofH2Ocondensed on gold foil. The results demonstrate that PEPICO and AEPICO combined with SR are powerful methods for investigating the ion desorption induced by core-level excitations. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147978

出版商:AIP    

年代:1997

数据来源: AIP