摘要:

A double crystal x‐ray monochromator system has been developed for use on synchrotron radiation sources. The system consists of two separate Bragg reflecting crystals constrained by a mechanical linkage system enabling it to tune continuously in x‐ray energy, always maintaining an exit beam of constant offset and direction relative to the incident beam. Accurate parallelism between the two crystals is maintained by a piezoelectrically‐controlled analog feedback circuit.

ISSN:0034-6748    

DOI:10.1063/1.1136631

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A high‐resolution, angle‐resolved photoemission electron spectrometer has been built which incorporates a position‐sensitive multidetection system. The spectrometer is a 180 ° hemispherical electrostatic deflection analyzer utilizing preretardation, 1.5 ° angle‐resolving optics mounted on a two‐axis angular manipulator. Combined with the sample holder, independent control of the polar and azimuthal angles of both the sample and detector are available. The multidetection spectrometer collects through a PDP‐11 based data acquisition and control system up to 32 resolution elements per spectral frame.

ISSN:0034-6748    

DOI:10.1063/1.1136632

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A microwave spectrometer and associated apparatus for the detection of unstable free radical species is described. The spectrometer, which operates over a frequency range from 66 to 73 GHz, consists of a tunable Fabry–Perot resonator followed by superhetrodyne detection for high sensitivity at low power levels. The resonator tuning is accomplished by means of a computer‐controlled stepping motor and by a piezoelectric tranducer which also permits the use of source modulation and phase sensitive detection at 100 Hz. The sensitivity of the spectrometer is adequate to permit the detection of rotational transitions with absorption coefficients as small as 2×10−9cm−1. The operation of the spectrometer is demonstrated by the detection of the two free radical species OH and SO. In the case of OH, a number of L‐doubling transitions, previously unobserved, are reported.

ISSN:0034-6748    

DOI:10.1063/1.1136633

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The design and construction of an Overhauser Effect Spectrometer operating at X band is described. The ESR section is a Varian V‐4502 spectrometer equipped with a 9‐in. electromagnet and a shim coil assembly. NMR detection is based on a broadband rf hybrid juction feeding a coil in an X‐band quartz dielectric cavity. Signal processing is carried out at a constant intermediate frequency of 25.1 MHz with a Varian V‐4311 fixed frequency rf unit. The mixing scheme employed to translate the NMR information to 25.1 MHz is described. Medium resolution performance (resolution ∼10−6) for the NMR is achieved under field‐frequency locked conditions. The lock is based on a Super‐Regenerative Oscillator (SRO) housing a control sample, and operating as a field‐tracking frequency source. This SRO injects into an oscillator which excites the analytical sample resonance and also serves as a local oscillator, thereby making the locked spectrometer multinuclear in capability. Typical Overhauser effect recordings of protons and fluorines are presented.

ISSN:0034-6748    

DOI:10.1063/1.1136634

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A 9.5‐GHz electron spin resonance ESR spectrometer which operates in conjuction with a helium dilution refrigerator down to 54 mK is described. Instead of the conventional waveguide and cavity arrangement, coaxial and superconducting twisted pair transmission lines are used to bring the microwave power into the mixing chamber, where a tiny coil surrounds the sample. This lowQ, high‐filling factor configuration has a sensitivity about the same as that of a conventional highQcavity with a small filling factor. Several suggestions for further development and improvement are presented.

ISSN:0034-6748    

DOI:10.1063/1.1136635

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

This paper presents an easy‐to‐build Fourier multinuclear magnetic resonance spectrometer operating, in the present case, below 100 MHz but readily adaptable to any magnet system. Receiver and transmitter are essentially made of commercially available wide‐band components. Some dedicated homemade circuits, necessary to the proper operation of the system, are described. A probe head has been especially designed for the observation of nuclei resonating between 6 and 36 MHz (nitrogen 14 to phosphorus 31), in addition to proton and fluorine (90 MHz and 84.6 MHz), without removing the sample and/or changing the spectrometer configuration. Interchangeable inserts are built in such a way that the measuring channel on the one hand, and the stabilization–decoupler channels on the other hand, are separated through the use of two orthogonal coils. Tuning and matching networks, which involve, for the measuring channel, homemade nonmagnetic capacitors variable in a large range, are described. The flexibility and the ease of operation of the apparatus are outlined.

ISSN:0034-6748    

DOI:10.1063/1.1136636

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A broadband probe having a tuning range of 20 to 65 MHz has been designed and built specifically to give maximum sensitivity per unit volume of sample. This is accomplished through use of a solenoid rf coil instead of the usual Helmholtz coil found in commercial probes for superconducting magnet systems. Improvement in signal‐to‐noise ratios approaches a factor of 3. Probe design considerations and construction materials are described.

ISSN:0034-6748    

DOI:10.1063/1.1136637

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

An instrument to measure the rotational and vibrational energies of heterogeneous reaction products has been constructed. Reactant atoms pass through a membrane made of the material being studied. After recombination and desorption occurs, the product gas is analyzed via either electron beam or laser‐induced fluorescence. Surface composition is monitored by soft x‐ray appearance potential spectroscopy. Results for nitrogen molecule desorption from clean, polycrystalline iron are presented in order to illustrate the capabilities of the apparatus.

ISSN:0034-6748    

DOI:10.1063/1.1136638

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The design and the operation of a continuous flow reflux (CFR) oven used for the formation of an effusive Cs molecular beam which is compatible with ultrahigh vacuum (10−9Torr) conditions are described. The CFR oven operation utilizes capillary action to recycle the unused part of the Cs molecular beam. A possibility of extending the principle to supersonic beam pressures is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1136639

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A fully engineered liquid metal field emission source of gold ions has been developed, operating with low heater power (<30 W) and without forced cooling. The design and performance of the source are described in detail. The present design can also be used to produce sources of a variety of elements, other than gold, including tin, bismuth, and lead. It provides a versatile and reliable research tool which is fully compatible with ultrahigh vacuum installations. Potential fields of application include materials development and surface analysis.

ISSN:0034-6748    

DOI:10.1063/1.1136640

出版商:AIP    

年代:1981

数据来源: AIP