Charge-State Dependence ofK-Shell-Vacancy Production Cross Sections in Slow Ion-Atom Collisions

Abstract

one count an hour c This is close to being reasonable, since much of the desired phase space could be collected simultaneously,, We conclude that the K + meson would theoretically provide an excellent probe of the deep hole states via knockout. The effects of distortion should be much less than in (p, 2p) reactions. The cross sections are larger than those observed in (e,e'p) reactions, but the availability of highflux electron beams tends to give the electron reaction the advantage at the present time. Fluxes of K* mesons of the order of 10 7 -10 8 per second would make this experiment possible and would add a valuable tool to our current collection of probes of the nucleus.We would like to thank Carl Dover, Phil Roos, and Phil Steinberg for useful discussions. The computing time provided by the Ohio University Computer Center is gratefully acknowledged,, One of us (R.D.K.) would like tcr acknowledge the hospitality of the University of Maryland, where some of this work was performed. This work was supported in part by the National Science Foundation and the U. S. Energy Research and Development Administration. 1 G. Jacob and Th. A. J. Maris, Rev. Mod. Phys. 45,In low-velocity ion-atom collisions the production of if-shell vacancies via rotational coupling of the 2p(j-2pTi molecular orbitals (MO), transiently formed during the collision, has been an area of extensive investigation. From the beginning of these studies one of the best evidences for the molecular picture of these collisions was the dependence of the inner-shell-vacancy production on the charge state of the incident projectile. For example, in Ne-~Ne collisions the cross section 6 (1973); private communication.15 P. G. Roos, private communication.was predicted and observed to double in going from 1 + to 2 + projectiles. 1 This was in agreement with the MO picture since the number of 2pn vacancies, and hence the K-shell-vacancy production cross section, was predicted to be proportional to the projectile charge state. A series of calculations 2 of if-shell-vacancy production via rotational coupling of the 2pv-2pir MO proved to be in agreement with the measured K-shell-vacancy production cross sections. 3 However, as K-shell-vacancy production cross sections in Ne-* CH 4 ,N 2 ,0 2 ,Ne and N--CH 4 ,N 2 ,0 28 Ne collisions are measured for incident charge states 1 + to 4 + and 1 + to 3 + , respectively, in the projectile energy range 50 to 500 keV. The data indicate there is a real deviation between experiment and the calculations of rotational-coupling cross sections. The data suggest that the deviations are not due to a nonstatistical distribution of the 2p vacancies among the 2p-n molecular orbital or a velocity-dependent coupling N(v) as has been previously assumed. 1322

Energy and technology review

“…Because we were no longer constrained by the limited resolution capability of the human eye, 4 ' 5 we could use a highresolution lens developed for exacting tasks in the manufacture of integratedcircuit photomasks. This lens has a focal length of 30 mm, an aperture ratio of f/1.2 and, in its standard configuration, a magnification of 25 diameters.…”

“…Figure S presents the results of a typical experiment to test the theory of rotational coupling. 5 In this case, we bombarded methane gas with neon ions with electronic charge up to +4 and measured the relative cross section tj n for K-vacancy production in both carbon and neon. According to the molecular or bital model, the relative cross section should be proportional to the number of L vacancies in neon (i.e., 1, 2, 3 or 4 for the different neon ions used), and this is what happens (Fig, 3a).…”

“…At present, the most powerful ac celerator of this type is the 50-MeV, 10-kA Advanced Test Accelerator (ATA) now under construction at LLNL. 5 A 1.1-GeV, 20-kA linear induction ac celerator would require a significant ad vance over the ATA with regard to voltage and emittance. (Emittance is related to both the degree of synchronism achievable and to the fraction of electrons in a cluster that end up in the decelerating bucket.)…”