摘要:

The problem of coincidence reflections with a Bragg peak is discussed and an apparatus is described for an automatic averaging over the ``umweganregung'' and ``aufhellung'' peaks to come very close to the true Bragg intensity. Results of an experiment are considered to prove the validity of the method. A refrigerator arrangement is described for work below room temperature.

ISSN:0034-6748    

DOI:10.1063/1.1684230

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Double beam (dual wavelength) spectrophotometers generally employ alternating, rather than simultaneous, illumination of a single sample with wavelengths &lgr;1and &lgr;2to secure large aperture viewing without optical cross‐talk. Although this technique allows the use of phase sensitive detection, which greatly reduces the effect of noise entering the system between light switch and demodulator, it also impairs the system's immunity to lamp noise, as compared to a true differential system, in which &lgr;1and &lgr;2simultaneously illuminate the sample. To improve the noise rejection, we have devised a method of compensation which uses a second photomultiplier to monitor the time shared light beam before it enters the sample. The resulting signal is normalized and subtracted from the measure signal in a differential amplifier over a bandwidth including frequencies considerably above the switching frequencyfc. Details of design are presented together with experimental data showing that greatly improved performance can be obtained with 450 W xenon and AH‐6 type 1000 W mercury arc lamps. In the latter case a 20‐fold decrease of low frequency noise is obtained at 280 nm.

ISSN:0034-6748    

DOI:10.1063/1.1684232

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

We describe a sample holder useful for the study of the angular dependence of photoluminescence at liquid helium temperatures. The system is characterized by a high collection efficiency and is particularly well suited to situations where there is only vertical access to the experimental space.

ISSN:0034-6748    

DOI:10.1063/1.1684233

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

The electrostatic quadrupole field can be applied as an energy filter using the telescopic trajectories in a plane normal to the hyperbolic electrodes. Particle dynamics, focusing properties, and energy dispersion are given for instruments with cylindrical or rotational symmetry. The cylindrically symmetric field has unidirectional focusing of the second order, while the rotationally symmetric field has bidirectional focusing of the second order.

ISSN:0034-6748    

DOI:10.1063/1.1684234

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Saddle shaped coils for generating a field perpendicular to the axis of a cylindrical shell to which the coils are confined can be designed in a compact and easily constructed form. The central magnetic field of such a system and its second derivatives with respect to displacements from the center are given as functions of the coil dimensions, and conditions for minimizing these derivatives are discussed. A coil pair with a length‐to‐diameter ratio of 2 and circular arcs of 120° will have no second order central field derivatives in any direction.

ISSN:0034-6748    

DOI:10.1063/1.1684235

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Three analytic ultracentrifuges are controlled and useful operating measurements recorded by a central control and data acquisition system. Rotor speed, temperature, picture number of each schlieren photograph, and time of each measurement are recorded on cards by a printing summary punch machine. AFortranIV computer program processes the data, yielding graphs of rotor speed and temperature vs time and the accumulated value of&ohgr;FS−2∫&ohgr;2(t)dtfor the mean time of each schlieren photograph. These data permit error detection as well as more accurate schlieren analysis of lipoprotein distributions and flotation rates.

ISSN:0034-6748    

DOI:10.1063/1.1684236

出版商:AIP    

年代:1970

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1684237

出版商:AIP    

年代:1970

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1684238

出版商:AIP    

年代:1970

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1684239

出版商:AIP    

年代:1970

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1684240

出版商:AIP    

年代:1970

数据来源: AIP