摘要:

Required microscope conditions and the technique of photography and development procedures are described, and means of improvement suggested for high resolution, high magnification 16 mm cinematography of chemical reactions at high temperature in the electron microscope. It is shown experimentally that, even with an externally mounted camera, resolutions of 12–15 Å can be achieved in practice at reaction temperatures of 1000–1100°C and magnifications of 110 000 × on the microscope fluorescent screen. Standard 16 mm reversal film exposed at 2 frames/ sec for 0.2 sec/frame andf/1.8 lens aperture are adequate but require accurately controlled development conditions. It is therefore shown quantitatively that it is possible to obtain higher resolution at shorter exposure times by photographic means than by more complicated and more costly electronic equipment. Standard electron microscope movie attachments were considered but vibration alone prohibits their use for high resolution recording. Photographic grain structure remains the major factor limiting high resolution cinematographic recording in the electron microscope. Reaction is observed between MgO and the Pd specimen support grid. A phase behaving like a liquid forms and extends over the surface, stripping the crystal via a surface mechanism, changing shape and contracting back into the main body of the phase.

ISSN:0034-6748    

DOI:10.1063/1.1684412

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A small, easily constructed, and high efficiency Bragg angle x‐ray spectrometer has been developed. Employing either a lead stearate or a KAP crystal, it has been used to measure x rays in the 150–1000 eV region from ion‐atom collisions. At the carbon‐K energy (277 eV), it has an FWHM of 14 eV and an efficiency of 10−2counts per incident x ray. Electronics and controls for fully automatic scans are described.

ISSN:0034-6748    

DOI:10.1063/1.1684413

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

We have demonstrated the feasibility of using polarization coding in an interferometric measurement of optical phase. Phase variations can be followed continuously, relative to the beginning of any desired time interval. Typical phase fluctuations of a laser beam traversing the open turbulent atmosphere are presented.

ISSN:0034-6748    

DOI:10.1063/1.1684414

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A method is described for measurement of low energy total cross sections using an analysis of the uncollided portion of the beam by electrostatic repulsion. Instead of energy separation of the initial beam, a (retarded) spectrum of energies (0–10 eV) is accepted and analyzed with and without interactions. The method applies, in principle, to energies arbitrarily close to zero, limitations occurring in beam intensity and in the smallness of energy group treated in the associated computer analysis. A further limitation is that only large angle scattering is measured. Test measurements for argon ions in argon gas show total cross sections above 1 eV to be indistinguishable from quoted values of charge transfer. In the vicinity of 1 eV a steep rise in cross section is observed.

ISSN:0034-6748    

DOI:10.1063/1.1684415

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A simple, nondispersive spectrometer has been designed which allows the binding energies of core electrons to be determined for atoms at a solid surface. The spectrometer consists of a photomultiplier which measures the total soft x‐ray fluorescence of the anode surface of a vacuum diode. The derivative of the multiplier current as a function of the anode potential rises abruptly at the appearance potentials of characteristic x rays. The derivative is taken by superimposing a small oscillation on the anode potential and synchronously detecting the variation in multiplier current. The information obtained is comparable to that usually derived from absorption spectroscopy but is much more sensitive to the surface region. Thus, in addition to determining the elemental composition of the surface, chemical shifts in the binding energies of core electrons are readily observed.

ISSN:0034-6748    

DOI:10.1063/1.1684416

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

The field ion microscope atom probe makes possible the chemical identification of individual atoms field desorbed from a sharp metal tip by time of flight along a drift tube. An instrument to control the rate at which desorption pulses are applied and to record the resulting data is described. Rates of a few hundred pulses per second are readily achieved, and the instrument can be programmed to terminate either after a present number of cycles or in response to the acquisition of the first piece of data. This latter mode of operation is particularly convenient for establishing the best field desorption conditions. Resolution of adjacent mass numbers depends on the time resolution of the instrument; the best time resolution achieved is 40 nsec, resulting in a mass resolution of about 1% for typical ion travel times.

ISSN:0034-6748    

DOI:10.1063/1.1684417

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Measurement of sheet resistances of high resistance (up to 1016&OHgr;/□) thin films using conventional methods is both difficult and subject to error. We have developed a method for making sheet resistance measurements in which a low velocity electron beam is used to inject charge into the film. The injected charge drifts under the influence of its self‐induced field to metal electrodes evaporated on the film, where it is collected and measured externally as a time dependent current. We give examples of thin GaAs films for which the measured current can be fit with a current predicted by a simple model over many orders of magnitude by adjusting only one parameter, the sheet resistance of the film. The good agreement between experimental and theoretical currents provides reliable values for the sheet resistance. This allows an estimation of a lower limit on the carrier density native to our GaAs films.

ISSN:0034-6748    

DOI:10.1063/1.1684418

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Determination of relative heights from SEM stereo photographs is considered. It is shown that by the choice of suitable geometry it is possible to derive exact formulas for both the case of translating and tilting the specimen. The translation method is shown to be useful for determining the true working distance whereas the tilting method is more sensitive to small height differences. A comparison between exact and approximate (infinite working distance) formulas is made in the specimen tilting case. Experimental requirements are considered and methods are suggested.

ISSN:0034-6748    

DOI:10.1063/1.1684419

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A small computer data system was constructed and evaluated for use with a portable quadrupole mass filter. The system is composed of two conventional audio tape decks, one interfaced to the portable mass filter and the other to a small shared computer. In operation, a series of mass spectra is recorded on magnetic tape. Next, the tape is transferred to the audio tape deck interfaced to the computer. The computer adds the spectra together and performs appropriate spectrum stripping and arithmetic routines. By reexamining hydrogen‐deuterium self‐exchange in water, we show that the mass filter‐recorder‐computer system gives results that are as accurate and precise as results obtained from other mass spectrometric methods.

ISSN:0034-6748    

DOI:10.1063/1.1684420

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A method is described for the measurement of characteristics of pickup electrodes (PUE) for monitoring coordinates of an accelerator beam. A new representation is discussed for determining the coordinates of the center of charge for the entire PUE aperture. A few prototypes of PUE's to be installed in the AGS were tested and the results show that nonlinear deviations are at least 1 mm/25 mm. The method of measurement has a resolution of at least 0.1 mm/25 mm; it can therefore be used for (a) the design of high quality PUE's and (b) calibration of PUE's as installed in the accelerator in order to increase the usable aperture and the accuracy of beam coordinate monitoring.

ISSN:0034-6748    

DOI:10.1063/1.1684421

出版商:AIP    

年代:1970

数据来源: AIP