The neon Auger spectrum produced by ion bombardment of aluminium and silicon surfaces

Abstract

AbstracL Measurements are rrrpocied at the hger (autaimizatian) peer rum of tie produced b j bombarding Al and Si surfaces with Ne4 ions with energies in the range 4Nl eV lo 5 keV l l e shift in the Ne peak energies with incident ion energy is shown to follow a wry simple Doppler model. ?ne data are found 10 mntsin many mall Auger peab in nddition b the two characteristic peaks rearded ly prwious wakcrs. Ttis new sliuclun ir shown to t x mnsistent with gas-phase data and with measurements of the auloionhing mles m Ne I.

Charge exchange and excitation in collision at medium energy (2-30 keV). Experiment and simulation

“…In a recent paper Ascione et al [22] measured the discrete energy loss of Ne 2+ ; their value of 85-87 eV is in agreement with previous results of Wittmaack [23]. This energy loss corresponds to the ionization plus excitation of a surviving Ne + in the close collision; this Ne 2+ * ion decays directly into the Ne 2+ ground state or through electron capture into Ne + * * followed by autoionization (this autoionization is responsible for the low intensity electron line observed at 30.4 eV [24]). This process implies that some of the incoming ions should not be neutralized until the hard collision event; this seems to be likely for primary energy exceeding 5 keV as we will show below.…”

“…At higher energies we observe two smaller peaks which can be assigned to 2p 4 ( 1 D)[3s3p( 3 P)] 3 F (26.2 eV) (c) and 2p 4 ( 1 D)[3s3p( 1 P)] 1 P,D,F (28.1 eV) (d). These lines correspond to those labelled 1, 3, 4, 6 by Gallon and Nixon [24].…”

“…In the case of a doubly excited ion Ne + * * (2p 3 nl n l ), an autoionizing state with a triplet or a singlet core could be produced through Auger or resonant capture with the same probability [21]. Doubly excited ions can directly autoionize into doubly charged Ne ions; this process has been confirmed by the observation of a very small line at 30.4 eV in the autoionization spectra of Ne on Al and Si [24,33] and by the value of the inelastic collisional energy loss of Ne 2+ ions produced in Ne + -Al and Si collisions [22,23]. When the projectile becomes more energetic, these quasi-direct processes compensate the loss of efficiency of the core rearrangement processes due to the increase of the perpendicular velocity.…”

“…The autoionization lines from Ne * * represent only a very small part of the total electron production but they are the most direct proof of the important role of the electron promotion mechanism in the close collision. Starting from the gas phase electron or ion collision data [29,30], many identifications have been made in the case of collisions of Ne with surfaces [6,24,28,31]. The two most important lines at 20.45 (a) and 23.70 eV (b) are attributed to the 2p 4 ( 3 P)3s 2 and 2p 4 ( 1 D)3s 2 Ne * * states decaying in vacuum into Ne + 2p 5 .…”

Contribution of singly and doubly ionized argon to the autoionization (Auger) spectrum of argon excited by bombardment of magnesium and scandium surfaces

“…The electron spectrum of Ne produced when Ne ions bombard solid targets of elements such as Mg or Al at the start of the third period shows considerable fine structure which is broadly similar to the spectra obtained in the case of gas phase collisions [1][2][3]. Exact details of the excitation mechanism remain to be clarified but the spectra can be indexed largely in terms of collisionally excited processes in Ne * * with two 2p electrons promoted to autoionizing states.…”