Knight ShiftsKV,KTc, and

D. O. Van Ostenburg

¹

,

D. J. Lam

²

,

H. D. Trapp

³

et al.

Abstract

the delay in response between a pair of probes and the other on the time that elapsed before each individual probe responded. Both methods indicate the same result, namely, a speed of plasma expansion of about 10 4 cm sec" 1 . In contrast, the calculated wave velocity for the propagation of electroacoustic waves in the plasma would be about 10 6 cm sec" 1 .The evidence for the slow expansion of the plasma column rests solely on the probe signals. Such slow motion in the absence of an external magnetic field has been unknown hitherto, so it is natural to suspect the probes. There is no evidence as yet to support this suspicion: For example, in one run during which the probes responded at different times as usual, there was subsequently a break in the discharge currentIn bcc V-Tc-Al alloys the conduction electrons of V and of Tc form a common band, according to measurements of the magnetic susceptibility and nuclear magnetic resonance of the alloys, whereas the conduction electrons of the Al interact but little, if at all, with those of the transition elements. For the V and Tc these results agree with the previously reported behavior of bcc binary alloys of V with other transition metals 1 of the first and second long periods. Since the composition dependence of the Knight shift and magnetic susceptibility of these binary alloys depend essentially on the electron/atom ratio rather than on the alloying species, these elements appear to conform to the rigid-band model; that is, the number of electrons in the band of an element in the periodic table is simply increased or decreased by alloying with a neighboring element without appreciably affecting the band structure. Measurements of low-temperature specific heats 2 and of superconductive transition temperature 3 likewise imply applicability of the rigid-band model to bcc alloys of the first and second long-period transition elements.On the other hand alloying V with nontransition elements, 4 such as Al or Si, changes the which was not maintained. The collection of current by all the probes then ceased simultaneously.At this preliminary stage of the investigation it would be premature to offer an explanation of the slow expansion. However, it is certain that it is not an aerodynamic effect related to the ejection; the neutral particles reached the ionization gauge much more quickly than the charged particles reached probes situated closer to the exposed plasma column than the gauge. It is possible that the effect is associated with the stability of the plasma sheath and that some form of electrostatic confinement retards the motion of the plasma.A more detailed account has been submitted for publication elsewhere.picture. For example, in the V-Al binary bcc system, the V 51 shift increases only slightly from 0. 56% in pure V to 0. 58% at 40 at.% Al in V, and the change is nearly linear with Al content. The Al 27 shift is negative and nearly independent of concentration within experimental error, with a value in the vicinity of -0.03%. This is to be contrasted with t...