Resolution dependence and asymmetry of electron capture to the continuum spectra

Meckbach, W.; Nemirovsky, I. B.; Garibotti, C. R.

doi:10.1103/physreva.24.1793

Cited by 125 publications

(35 citation statements)

References 23 publications

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“…The ridge-shaped structure joining the SE and ECC peak continues, with increasing i\ into the well-known negative skewness of the ECC cusp [16], and with decreasing t», into the now discovered positive skewness of the SE peak. It is then not surprising that both these asymmetries are of the same order of magnitude.…”

Section: Experimental Evidence Of the Asymmetry Of The Soft Electron mentioning

confidence: 90%

Experimental evidence of the asymmetry of the soft electron peak in ion-atom ionization

et al. 1993

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We have measured the doubly differential energy and angular distribution of low-energy electrons emitted in collisions of H + and 3 He 2+ on Ne at 106 keV/u. In this way, we are able to obtain information about the shape of the soft electron ionization peak. Against current belief, but in accordance with a two-Coulomb-center interaction of the emitted electron, we find it to be strongly asymmetric in the forward-backward direction. We discuss the shape of the cross section and introduce a parametric expression for fitting the data.PACS numbers: 34.50.FaThere is no doubt about the existence of a strong soft electron (SE) peak in the spectra of electrons emitted in ion-atom collisions. The corresponding cross section do/dv, doubly differential in the direction and modulus of the electron velocity (v), is expected to have a l/v divergence in the limit v-• 0. Consequently, the energy distribution dcr/dEdfi should be a smooth function for small electron energies (E). Until now, no measurements have been presented that permit a discussion of the shape of the SE peak, mainly because of the well-known experimental difficulties for the accurate analysis of electrons propagating with small velocities.The SE peak is one of the three important features of the spectra which give direct evidence of the electron-ion Coulomb interaction, in ion-atom and atom-atom ionization. Meanwhile much attention has been paid to the two remaining reactions, i.e., electron capture to the continuum (ECC) and electron loss to the continuum (ELC). This paper is the first attempt to study the shape of the SE peak.Fast collisions accompanied with small momentum transfer are usually treated with the first Born approximation (FBA), in which the triply differential cross section (TDCS), differential in the velocity (v) of the emitted electron and momentum transfer (K) of the scattered bare ionic projectile, is given (in atomic units) by [1] where/ V ,/(K) is the generalized oscillator strength. Here Z and V are the charge and initial velocity of the projectile, K the momentum transfer during the collision, and Ei the energy of the initial bound target state, with quantum numbers i =« ,/,ra.The oscillator strength can be expanded in spherical harmonics, giving [2] /*,/ -X^/G>,*)/V(cos0 K ) ,J where #K is the angle between v and K. The doubly differential cross section (DDCS) in the velocity v is obtained by integration on K and gives [2]L where 0 is the angle between V and v. We write explicitly the \/v divergence associated with the asymptotic Coulomb potential of the residual target ion. For a \s initial state and a Coulomb final wave for the electron, Eq. (3) can be written as a double series expansion [3,4],which, within the considered FBA, has the constraint B[ k) =0 for k+L odd and for L > k + 2. For a generic initial state Burgdorfer et al. [5] studied the limit v-• 0 of Eq. (3) and obtained a finite expansion In da/dv = (\/v) S C L (i 9 V,v-0)P L (cosO) 9 (5) L(cven)where CLU,V,V =0) =2?i 0) . For a \s initial state only two multipoles contrib...

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Section: Experimental Evidence Of the Asymmetry Of The Soft Electron mentioning

confidence: 90%

Experimental evidence of the asymmetry of the soft electron peak in ion-atom ionization

et al. 1993

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“…This asymmetry of the ECC and EEC cusps has been the subject of intense research in ion-atom collisions for many years [23][24][25][26][27][28].…”

Section: Asymmetry In the Ecc Cuspmentioning

confidence: 99%

Dynamics of collisions with positrons

Fiol

Macri

Barrachina

2009

Nuclear Instruments and Methods in Physics Research Section B:

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“…The cusp anisotropy then became a subject of much intera the cusp ani tum number made extens ow theories two electron decayed by to subsidary foht (22) (19) developed expressions that connect the cusp anistropy with the density matrix of states of high principal quantum number produced by electron capture. Meckbach (20), amoung others, made extensive measurements of the cusp angular distribution to probe various theories (21) of ionization. Harrison and Lucas (9) and others noted that two electrons could be captured into autoionizing states.…”

Section: Other Developmentsmentioning

confidence: 99%

Electron transfer to continuum states

Macek¹

1996

AIP Conference Proceedings

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O S -r ,Gene Rudd's analysis of doubly differential crom sections for the ionization of He atoms by proton impact suggested that electrons were being carried along by the proton for a short period of time after being ejected fiom the target region. Normally, this would represent an electron capture event in which an excited state of atomic hydrogen is formed. Because the electron ends up ionized it was recognized that these states of the proton must be continuum states. This insight was confirmed by observations of the continuum electron capture (CEC) cusp when the electron velocity equals the proton velocity in the final state. The impact of this idea upon the theory of ionization at high enereies is reviewed.

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Resolution dependence and asymmetry of electron capture to the continuum spectra

Cited by 125 publications

References 23 publications

Experimental evidence of the asymmetry of the soft electron peak in ion-atom ionization

Experimental evidence of the asymmetry of the soft electron peak in ion-atom ionization

Dynamics of collisions with positrons

Electron transfer to continuum states

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