Experimental Investigation about the Mechanism of Fission-Fragment Induced Desorption

Abstract

The physical processes involved in the fission-fragment induced desorption of molecular and atomic ions from surfaces have been investigated by measuring absolute ion yields, distributions of radial and axial initial energy components and isotopic effects. For this purpose several modifications of the time-of-flight spectrometer were put in practice. By studying multiple ion desorption per fission-fragment correlations between various molecular fragments were identified. The results are compared with predictions of reaction models. The observed phenomena are in agreement with a break-down of the polar-binding potential at the surface caused partially by the low energy electron plasma produced by the fission-fragment.

Thermodynamics of Ion Formation by Fast Dissipation of Energy at Solid Surfaces

“…As this recapture parameter r is also relevant for the kinetic energy distribution as discussed in Chapter 3.1, both distributions depend from each other. This has been shown to be valid for FFID by the investigations of Fürstenau and Knippelberg [16].…”

“…dX may be written as Y^A max 1 tot (31) according to (16) and (17), with a total interaction probability of the high-frequent perturbation with a main frequency co" (co n oscillator frequencies (infrared) of the molecule). The probability P tot can be described as the linear response of the system of the co' n due to the perturbation F, which is given by a set of amplitudes a n (co' n ), which may be modeled by the light extinction coefficient of light frequency co' as an electric interaction strength.…”

High Energy Sputtering from Cleaned Metal Foils

“…So far fission fragment induced desorption has always been studied by time-of-flight (= TOF) spectrometry, which turned out to be very suitable for taking mass spectra but also for measuring energy and angular distributions of the emitted secondary ions [10]. The high energetic primary ions are delivered by the spontaneous fission source 252 Cf.…”

“…The principal of the TOF technique concerning fission fragment induced desorption has been described elsewhere [1,10,11]. The sample holder is inserted into a stainless steel sheet providing a flat plane for the surroundings of the sample.…”

“…The start and the stop detector have been described in Ref. [10] and [11]. The latter one is mounted at a flight distance of 23.0 cm providing maximum acceptance for all emitted ions at an acceleration voltage above 1 kV.…”