摘要:

Correlations of the important parameters of the BCS theory of superconductivity are developed with respect to the number ofd‐shell electrons per atom of the transition elements predicted by the Engel‐Brewer theory of alloys. The importance of ``bonding'' on thedlevel as a generalized electron‐electron interaction is demonstrated; and the total attractive potentialVof the BCS equation for the critical temperatureTcis shown to arise from both the phonon‐induced potential,Vph, and a large attractive potentialVb, due to bonding and having a maximum at the half‐filleddshell. The present theory is consistent with the recent data of amorphous superconductors if their electron density of states at the Fermi level,No, is a constant or a shallow function of the electron‐per‐atom ratio. The anomalous isotope effect of some elements is also discussed, as well as the fundamental instability of high‐Tcsuperconductors and the incompatibility of ferromagnetism and superconductivity.

ISSN:0021-8979    

DOI:10.1063/1.1663508

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The x‐ray absorption coefficients of the metals Al, Ti, Fe, Ni, Cu, and Zn have been measured for radiations in the 1.5–3‐keV range. Monochromatic x rays were obtained by diffracting characteristic x‐ray lines with a crystal. Freedom from fluorescent radiation was ensured by using crystals of low‐Zmaterial. The absorber thicknesses as well as the time distributions between measuringIandI0were optimized. The average of nine transmission measurements taken with the absorber in nine different positions was used in computing the absorption coefficients for each element. Comparison of absorption coefficients obtained with different absorbers of the same element indicates an experimental uncertainty of 1–4%.

ISSN:0021-8979    

DOI:10.1063/1.1663509

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Implicit in the use of nuclear backscattering as a quantitative analytic tool is the accuracy of calculating cross sections using a classical Coulombic scattering formula (Rutherford cross section) which includes recoil effects, but ignores spin, nuclear size, electron screening, hard‐sphere scattering, and any nuclear‐force effects. The Rutherford cross section has not previously been verified experimentally for ions of4He (1–2.5 MeV) for targets of16O,27Al, and28Si. For14N, agreement has been found with an accuracy of about 5%. Our experimental results show that27Al and28Si have the Rutherford formula value (±1%), and16O is Rutherford from 1.4 to 2.4 MeV.14N appears to deviate by about 2% at energies from 1.2 to 2.2 MeV and by more beyond this energy band.

ISSN:0021-8979    

DOI:10.1063/1.1663510

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

High‐resolution medical radiographs have been produced with a laser‐generated plasma x‐ray source. The nanosecond pulse width is capable of arresting biological motion. In addition, the soft x rays from this source have been transmitted through a new type of x‐ray beam handling device, the x‐ray pipe, which is an x‐ray analogue of the conventional light pipe. This may allow new medical applications such as channeling soft x rays to internal locations of the body without damaging intervening tissue.

ISSN:0021-8979    

DOI:10.1063/1.1663511

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The statistical behavior of the amplitude probability density for 1/fnoise from carbon resistors has been investigated both experimentally and theoretically. It is found that some carbon resistors exhibit a 1/fnoise which is in agreement with the behavior expected for a stationary normally distributed process, while other carbon resistors exhibit a type of pulse noise in addition to 1/fnoise which serves to modify the measured statistical properties of the noise. It is concluded that 1/fnoise itself is not significantly different from other noises in its statistical properties.

ISSN:0021-8979    

DOI:10.1063/1.1663512

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The problem of modeling random noise by a sequence of random pulses that result from the random occurrence of similar events of randomly varying duration and strength is considered. It is illustrated how the statistical properties of the distribution of noise‐producing events may be inferred from a knowledge of the power spectrum of the noise and the characteristic shape of the pulses.

ISSN:0021-8979    

DOI:10.1063/1.1663513

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Examination of solution‐grown KD*P single crystals by the Lang technique has shown that the crystals are free from growth veils, impurity segregation, and subgrain boundaries. The density of dislocations varies throughout the volume of the crystals, some areas being nearly dislocation free. One Burgers vector identified as being parallel to ⟨100⟩ is common to the similar KDP and ADP single crystals.

ISSN:0021-8979    

DOI:10.1063/1.1663514

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The combined effect of film thickness and grain size diameter on the temperature coefficient of resistance of a uniform continuous polycrystalline metal film of thickness greater than the intrinsic mean free path has been theoretically investigated. It has been found that the value of the temperature coefficient of resistance decreases with decrease in grain size. For very small grain size it is less than the bulk value and may be negative in some cases, whereas for very large grain size and film thickness it approaches the bulk value.

ISSN:0021-8979    

DOI:10.1063/1.1663515

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Using theR(30) N2O laser line in order to saturate the infrareds a Q(9, 6, 9) (v2= 0 ↔v2= 1) vibration‐rotation line of NH3, the inversion of the microwaveJ= 9,K= 6,M= 9,v2= 0, has been obtained. Exact coincidence between the laser line and the infrared NH3transition is realized by Stark‐effect tuning. The variation of the Stark field through the exact coincidence permits studying the evolution of the microwave line versus the frequency mismatch of the pumping radiation.

ISSN:0021-8979    

DOI:10.1063/1.1663516

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Experimental measurements of the electrical conductivity of thermally grown SiO2switched into a high‐conductance state are presented. Ap‐njunction formed under a non‐self‐healed breakdown filament is found to control the current of the high‐conductance state.

ISSN:0021-8979    

DOI:10.1063/1.1663517

出版商:AIP    

年代:1974

数据来源: AIP