摘要:

We report the construction of a low pressure (∼0.5 Torr) helium direct current discharge cell to lock a 1083 nm InGaAs diode laser to the 2 3S–2 3Ptransition in helium using saturated absorption spectroscopy. The direct current discharge cell has the advantage of being radio frequency noise free. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147420

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The technique of electric‐field‐induced second‐harmonic generation (EFISHG) has been extended by use of a femtosecond, quasi‐cw laser pump source. The effects of ultrashort pulse widths on the coherent EFISHG process have been examined and the analysis procedure used for nanosecond pulse EFISHG measurements is found to be suitable for femtosecond measurements in off‐resonant regions. A convenient method for measurement of the group velocity mismatch between the fundamental and second‐harmonic pulses in solutions has also been developed to accurately describe the femtosecond EFISHG process. Phase‐sensitive detection of the modulated second‐harmonic signals results in improvements in accuracy and sensitivity over existing nanosecond pulse experiments. This has been demonstrated with a measurement of &Ggr;(−2&ohgr;; &ohgr;, &ohgr;, 0) of an organic molecule, 4‐nitroanisole. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147421

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Several years ago a time‐resolved circular dichroism technique for the far ultraviolet spectral region with submicrosecond (10−7s) time resolution was developed using a xenon flash lamp probe source for measurements of circular dichroism (CD) signals. Recent improvements in Ti:sapphire lasers, providing the ability to frequency‐convert the fundamental outputs to produce second, third, and fourth harmonic pulses, allow single wavelength measurements of CD with nanosecond (10−9s) time resolution over a broad spectral region (205–910 nm). This provides a powerful technique to study fast biophysical phenomena such as protein folding processes. In this article, the methodology and preliminary application of this new technique are presented. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147422

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A novel high‐resolution surface sensing device is developed and demonstrated, which utilizes Bragg diffraction from the volume holograms in the photorefractive BaTiO3crystal. In this device, the angular information of a surface is obtained as a diffraction pattern from the multiplexed holograms stored in the crystal. The resolution of this device is as high as submilliradian due to the Bragg selectivity. Additionally, a new method of surface structure comparison between two samples is also demonstrated using this device, which is applicable to the nondestructive surface inspection of optical components. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147423

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We describe the construction and performance of a small‐angle x‐ray scattering (SAXS) instrument which we have used on several beam lines at the National Synchrotron Light Source. The analyzer crystal was a channel cut Si(1,1,1) designed for use at &lgr;=1.54 A˚ with a measured efficiency of 60% and an angular resolution full width at half maximum of 0.001°. In the case of strongly scattering samples (i.e., powders), momentum transferqbetween 1×10−4A˚<q<0.1 A˚−1could be studied with over eight decades of dynamic intensity range. We demonstrate the versatility of this instrument by performing scattering experiments on a variety of spherical latex samples spanning the size range from 50 to 800 nm, liquid crystal samples with sharp, asymmetrical Bragg peaks, and metal clusters with sizes less than 10 nm. Small‐angle x‐ray scattering data for the larger polystyrene samples is compared with light scattering data and theoretical structure factors, and the relative roles of instrument smearing, sample polydispersity, and interparticle interference are elucidated. In the case of the liquid crystal samples, the high resolution of the instrument allows structural features to be observed that were previously obscured by the instrumental resolution in other small‐angle neutron and synchroton‐based Kratky camera data taken on the same samples. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147424

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have developed a thyratron‐gated, high‐intensity nanosecond pulsed lamp using a commercially available Xe short‐arc lamp. A dc voltage higher than 10 kV is applied to the electrode gap through a high‐value resistor. A spark discharge in the electrode gap is generated by the trigger of the thyratron. Intense light pulses as large as 80 W (peak value) of 14–16 ns duration full width at half‐maximum was obtained repetitively from the Xe lamps. This lamp produced broadband emission spectrum (220–600 nm) according to discharge of Xe gas. Because discharge voltage of the pulsed lamp is much higher than that of a conventional dc lamp, a high electron‐temperature pulsed plasma is produced, resulting in enhancement of the UV component of the emitted light. The rich UV light from this lamp can be utilized as an excitation light source in time‐resolved spectroscopy. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147425

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

An attenuated total reflection (ATR) instrument for the observation of angle‐ and frequency‐scanned ATR spectra has been constructed. Light characterized by various wave vectors and dispersed into a spectrum has been detected by a charge coupled device camera after reflection from a rotating mirror and a diffraction grating. Two elliptic mirrors and a prism‐sample unit have been set between the rotating mirror and the diffraction grating for the purpose of controlling the light path. The images obtained have been analyzed by a digital image processing system so that angle‐scanned ATR signals are obtained for various wavelengths (500–800 nm). The time required to acquire one image has been 0.7 s in the present system. The dependence of the dielectric constant of a Ag film on wavelength is given here as an example measured by our system. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147426

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A new class of multiple dispersion grating spectrometer was commercialized a few years ago (SOPRA DMDP2000). In practice, mechanical tolerances do not let it operate at its very best characteristics. The instrument can be considerably improved by using a simple Michelson interferometer. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147427

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Synchronous wave number‐shift scanning of a Nd:YAG pumped dye laser and the detection monochromator for a coherent Stokes Raman scattering (CSRS) system were realized using an inexpensive analog to digital board. With this improvement the CSRS spectrometer may be used to scan over a large wave number shift range and/or may be used at relatively high resolution using a photomultiplier tube as the detector. This is especially useful in the probing of luminous systems. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147428

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The technique of forming a micro‐x‐ray beam with a fine capillary was studied. It was shown that lightweight materials, such as glass, were suitable for the capillary in terms of their x‐ray refractive indexes. A fine glass capillary with a parabolic cross‐sectional inner wall surface was made. Using the capillary, a fluorescent and diffracted x‐ray spectrometer with a 0.8‐&mgr;m‐&fgr; x‐ray beam was developed for the analysis of stress, crystal structure, and metal contamination in micro regions of ultra‐large‐scale integration (ULSI) devices. A micro‐focus x‐ray generator with a membrane‐type target was also developed for use with the capillary. The crystal phases of very thin Ti‐silicide fine lines and the strain in Al interconnections of ULSIs were analyzed using the equipment. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147429

出版商:AIP    

年代:1996

数据来源: AIP