摘要:

The fabrication and characterization of three near-field optical array types is presented. In all cases, a coherent fiber-optic bundle was chemically etched to produce an array of nanometer-sized, optical fiber tips. The270 &mgr;mdiameter bundle comprised∼6000tapered optical fibers and the smallest, etched optical fiber tips had an∼50 nmradius of curvature. This array could be metal coated, and a metal-coated array could be polished to yield an array of nanometer-sized apertures. These variable nanoarchitectures should be amenable to a large number of near-field scanning optical microscopies.©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147941

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A dc electron beam at 20 keV is used for the excitation of pure rare gases at pressures up to 1.7 bar. The well known second excimer continua of argon, krypton, and xenon observed under these excitation conditions provide an efficient light source in the vacuum ultraviolet spectral region between 120 and 200 nm. Thin (300 nm)SiNxfoils are used as entrance windows for the low energy electron beam. Due to the flexibility of the production process of the thin foils one can consider various shapes and sizes of the light emitting region to be manufactured. Efficiencies of∼30&percent;are observed for the conversion of electron beam energy into light. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147942

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An optical function pulse generator that emits (1) short pulse of 1 ns duration, (2) double pulse with variable time interval, and (3) square waveform pulse of variable width in nanosecond range is devised using an InGaN/AlGaN double heterostructure light emitting diode (LED). Although the LED emits a 450 nm (blue) light under conventional dc operation below 30 mA, 380 nm light due to the InGaN/AlGaN component appears when a current larger than 50 mA is applied. This phenomenon is used to realize a pulsed ultraviolet light source. Under large nanosecond current pulsing (peak current >1 A), an intense pulsed emission of 380 nm is obtained. Pulse waveform of the LED emission can be adjusted electrically by applying a shaped current to the LED. To evaluate the potential of the pulse generator as a test source of photodetectors, the response waveforms of photomultiplier tubes were measured. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147943

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Interference effects occur in the optical spectroscopy of thin film samples, and they can obliterate absorption spectra, especially if these are weak. A solution to this problem, originally proposed in 1976, is to place the sample inside an integrating sphere in the Edwards configuration so as to collect both reflected and transmitted light simultaneously. Surprisingly, the subsequent published literature on this technique is virtually nonexistent, despite its simplicity and effectiveness. This paper describes its use to measure absorption dips as weak as2×10−4in thin film samples. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147944

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Time-resolved natural and magnetic circular dichroism measurements on the nanosecond to second time scale have been used to investigate many chemical and biological processes. The key element that makes these measurements possible is a simple and inexpensive variable linear retarder (a strain plate) which produces well-characterized, elliptically polarized light throughout a broad spectral range (180–1500 nm). It essentially consists of a fused silica plate of high optical quality appropriately compressed from the edges to produce ∼1° of retardation. Early designs that consisted of a square plate compressed with wedges have worked satisfactorily in the past, but their use was complicated by inhomogeneity of strain across the probe beam (as large as 6 mm diameter for white light measurements with a flashlamp) and a temperature dependence of the strain. An improved strain plate that consists of a round fused silica plate compressed with springs is presented, and its performance is evaluated with respect to earlier designs. This improved strain plate not only simplifies time-resolved circular dichroism measurements but also improves the quality of the data and the kinetic resolution of intermediates. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147945

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The influence of different transparent conducting oxides (TCO) on the transverse photoelectrical properties of one-dimensional position sensitive detectors based onp-i-namorphous silicon structures was studied. For both SnO2and indium tin oxide, poor quality of theplayer was revealed by secondary ion mass spectroscopy measurements. Good agreement between experimental and simulation characteristics of TCO/p-i-nstructure was additionally conditioned by a strong increase in defect states at theplayer surface which can be attributed to the reduction/oxidation process at the TCO/pinterface. However, the analysis showed that under reverse bias the spectral response of thep-i-nstructure is not significantly affected by different TCO layers and conditions at the TCO/pheterojunction. Nevertheless, indium tin oxide is less appropriate for a front TCO layer due to the poor reverse dark current-voltage characteristic, i.e., higher leakage current component leading to lower signal to noise ratio. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147946

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The axial recoil approximation holds that when a diatomic molecular ion is formed in a dissociative state, the atoms produced in the dissociation process will move outward along the straight line defined by the internuclear axis of the molecule. Analysis of experiments measuring the angular distribution of Auger electrons emitted byN2followingK-shell ionization ofN2molecules shows that the axial recoil approximation is not strictly true. Significant corrections must be made for the rotation of the molecule during the time of dissociation. Smaller corrections must be made for the thermal distribution of the translational velocities of the target molecules, and for instrumental effects. In the analysis of theN2data, the corrections have the effect of smoothing the predicted angular distribution functions. The amount of the smoothing depends primarily on the temperature of the target gas and the shape of the potential-energy curve for theN22+final state involved in the Auger transition. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147588

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A new type of multiparticle three-dimensional imaging detector for the measurement of kinetic energy releases in molecular dissociation processes is presented. The detector makes use of the new generation of multianode photomultipliers to produce a timing signal for the simultaneous impact of several particles on the surface of a microchannel plate coupled to a phosphor screen. The detector is capable of subnanosecond time resolution (about 100 ps for the present setup) and position resolution (using a standard charge-coupled-device camera) of about 100 &mgr;m. The detector is suitable for ultrahigh-vacuum operation and can work with particles over a range of kinetic energies from keV to MeV. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147950

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A miniature quadrupole mass spectrometer array consisting of 16 rods in a 4×4 array is reported. Each rod is 25 mm in length and 2 mm in diameter. The ionizer is of a miniature Nier-type design, and the detector is a channel-type electron multiplier. Operating frequencies are 5.3, 7.1, and 12.9 MHz. The mass range demonstrated herein is 1–300 u; and the resolution of the system is 0.1–0.5 u (full width at half-maximum), orm/&Dgr;m=600. The present sensitivity is calculated and measured to be approximately1×1012counts/Torr s. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147947

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Axial energy spread and useful beam current of positive ion beams have been carried out using a radio frequency (rf)-driven multicusp ion source. Operating the source with a 13.56 MHz induction discharge, the axial energy spread is found to be approximately 3.2 eV. The extractable beam current of the rf-driven source is found to be comparable to that of filament-discharge sources. With a 0.6 mm diameter extraction aperture, a positive hydrogen ion beam current density of80  mA/cm2can be obtained at a rf input power of 2.5 kW. The expected source lifetime is much longer than that of filament discharges. ©1997 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1147948

出版商:AIP    

年代:1997

数据来源: AIP