The luminescence induced by the bombardment of thin molecular samples with single MeV atomic ions has been measured by time-correlated single photon counting. The MeV-energy ions (Z=6...79) were produced at the Erlangen tandem accelerator. The samples were layers of POPOP or CsI deposited on a thin polyester foil at a thickness which allows the ions to traverse the samples. The relative photon yield has been found to be proportional to the energy density along the ion trajectory when the initial velocity is kept constant. When the initial velocity of the primary ion was varied, a distinct maximum of the photon yield has been found which is clearly shifted to higher energies compared to the energy of the Bragg maximum. By means of calculations based on the energy deposition of the secondary electrons it was found that the observed luminescence is only produced in the region of low energy density at larger radial distances from the ion track.

First experimental results on the luminescence induced in thin molecular samples by the impact of single cluster ions Cn+ (n=2–10) at 1 MeV/atom have been reported. The cluster ions were produced and accelerated at the Erlangen tandem accelerator. The samples were a 1 μm CsI layer deposited onto a 2 μm aluminized polyester foil and a 100 nm POPOP layer prepared onto a 20 nm formvar film. The bombarding ions could traverse the samples but the cluster constituents did not remain in proximity in all cases. The luminescence was registrated by time-correlated single photon counting using either secondary electrons or transmitted clusters for starting the measurement. The relative photon yield obtained with clusters of various size increases linearly with the number of cluster constituents. The increase is less pronounced in case of the thin sample. This experimental result can be explained by the fact that the cluster ions leave the exit side of the sample as intact entities and that the photon emission is reduced in regions of high energy density.

It is shown by means of a few examples that MeV cluster ions from small accelerators are able to produce very high energy densities in matter, densities which are not accessible with the heaviest and fastest atomic ions from the big heavy ion facilities. The examples given are the pulse-height-defect in Si-detectors, defect production in mica and HTSC thin films, and cluster induced desorption of secondary ions.

Ultrathin rare earth oxide films have been fabricated using Langmuir-Blodgett films of rare earth arachidates as precursors. Irradiation of these films with UV light and subsequent heating of the films (350 degrees C) result in oxide films exhibiting a smoothness comparable to that of the Si-wafers used as substrates (roughness R approximate to 0.3 MI). The film thickness can easily be adjusted via the number of Langmuir-Blodgett monolayers deposited onto the substrate. (C) 1997 Published by Elsevier Science S.A.

MeV sputtering from CsI and organic samples induced by the polyatomic ions Cn+ (n = 1–12), Agn+ (n = 1–7), and Aun+ (n = 1–5) has been investigated. It is found that the desorption yield Yn increases more than linearly with increasing nonber n of projectile constituents. In case of the Cn+ induced desorption from a CsI sample it could be shown that the nonlinear increase of Yn reflects a linear increase of the energy density produced by the cluster projectile. This is a collective effect resulting from the simultaneous action of all n constituents of the polyatomic ion.

Polyatomic ions (cluster ions) can be accelerated to MeV energies using tandem accelerators. It is reported how cluster ions with greatly varying features (total mass, mass of the cluster constituents, number of cluster constituents, different ratios of nuclear and electronic energy losses) are produced and accelerated at the Erlangen tandem accelerator. Cluster ions available with energies up to 15 MeV are C-n(n = 2-10, 60) Al-n(n = 2-7) Ag-n(n = 2-7), Au-n(n = 2-5). The cluster ion intensities exceed 10(5) cm(-2) s(-1) in most cases allowing irradiation experiments where fluences of the order of 10(10)-10(11) cm(-2) are needed.

Bi2Sr2Ca1Cu2O8 + δ and YBa2Cu3O7 − δ thin films were irradiated by 23 MeV C60 and 24 MeV Au5 cluster ions from a tandem accelerator. The defect production of the C60 cluster ions in Bi2Sr2Ca1Cu2O8 + δ exceeds that of 238U ions with an energy of 2.7 GeV. The analysis of the mechanism underlying the defect production leads to different conclusions: (i) for C60 clusters we find independence of nuclear and electronic contributions to the defect production as in the case of atomic projectiles, (ii) for Au5 cluster ions this independence has lost it's validity. A possible interpretation of the Au5 results is that nuclear defects are annealed by the electronic energy loss. The size of the effective damage radii obtained for the Bi2Sr2Ca1Cu2O8 + δ film may indicate that continuous tracks are formed in this film via the C60 and Au5 irradiation.

The vacuum stability of Langmuir-Blodgett films consisting of fatty acids and Cd salts of fatty acids deposited on various substrates was investigated by means of plasma desorption mass spectrometry. Plain fatty acid films (particularly thin ones) exhibit a remarkable instability. Exceptions occur when the films are deposited on metal substrates covered with the natural oxide. In this case cation exchange occurs which results in the formation of salt (or a mixture of salt and acid) films exhibiting reasonable stability. Thin films consisting of 100% salt are fairly stable in vacuum.

Cation exchange taking place in Langmuir-Blodgett films of fatty acids deposited on hydrophobic Cu substrates was investigated by plasma desorption and spontaneous desorption mass spectrometry. Complete cation exchange was found in plain arachidic acid monolayers. Incomplete exchange was found in bilayer and multilayer films of Cd arachidate with thicknesses up to 10 monolayers. The fraction of exchanged ions is independent of the number of layers.

Atomic force microscopy (AFM) images taken from an Fe-arachidate Langmuir-Blodgett film irradiated with 23 MeV fullerene ions gives clear evidence that craters are formed as a result of the cluster-ion impact, The crater diameter fits into a systematic formula already found for atomic ions, The AFM images indicate that even the largest molecular ions desorbed stem from the crater volume.

The energy loss of small carbon clusters Cn (n = 2 − 5) with energies between 1.4 and 4.0 MeV in formvar, carbon and gold foils has been investigated. It is found that the energy loss of a cluster Cn with energy E0 is n times the energy loss of a carbon ion with energy E0n.

A novel molecular ion source based on the spontaneous desorption process has been investigated. The results obtained indicate that it is well suited for the analysis of organic molecules with masses up to 10(3) u in a time-of-flight mass spectrometer.

Yttrium arachidate multilayer films deposited on gold substrates by the usual Langmuir—Blodgett dipping technique have been investigated by means of Rutherford backscattering and plasma desorption mass spectrometry. It turns out that the cation of the film-forming molecules is Y3+. This is in contrast to a previous analysis where the cation was determined to be Y(OH)2+.

Langmuir-Blodgett (LB) films of fatty acid salts (Y-stearate, Y-arachidate, Cu-arachidate, Ba-stearate) were thermally oxidized. As a result one obtains ultrathin (a few Å thick) metal-oxide films at the substrate. The surface of the metal-oxide films was found to be rather inhomogeneous. Y and Cu ions remain quantitatively at the substrate despite the heating procedure. A linear dependence between area density of the metal ions in the oxidized films and the number of monolayers of the LB films was observed. The preparation of a mixed metal-oxide film containing Y, Ba, Cu with a given stoichiometry was found to be difficult due to the effect of counter ion exchange. The samples were investigated by means of plasma-desorption and spontaneous-desorption mass spectrometry, by Rutherford back-scattering and electron microscopy.

Ultrathin ferric oxide films (10(15) Fe ions cm(-2)) were prepared from Langmuir-Blodgett (LB) films of Fe arachidate. The LB films were heated for this purpose to a temperature of 300 degrees C. It turns out that the Fe ions remain quantitatively at the substrate during the heating procedure and that a linear dependence exists between the Fe area density in the ferric oxide film and the number of Fe arachidate monolayers. The homogeneity of the ferric oxide films was found not to be satisfactory if LB films with a small number of monolayers are used. The homogeneity increases with increasing number of monolayers. The analysis of the films was performed with mass spectrometric methods, Rutherford backscattering spectroscopy and electron microscopy.

Gold and C60 cluster ions have been accelerated to MeV energies with the EN tandem accelerator at Erlangen. Negatively charged cluster ions were produced in the sputter source and accelerated through both stages of the accelerator. The identification of the MeV cluster ions was performed by time-of-flight and energy measurements.

The conditions for complete salt formation of an arachidic acid monolayer spread onto an aqueous subphase were investigated by means of plasma desorption mass spectrometry in order to demonstrate that this method is very well suited to characterize Langmuir-Blodgett films. The combinations of subphase pH and metal ion concentration necessary for complete salt formation of arachidic acid monolayers were deduced from this analysis.

The observation recently made by Zubarev [R.A. Zubarev, P.V. Bonderanko, A.N. Knysh and B.V. Rozynov, Rapid Commun. Mass Spectrom., 5 (1991) 32; 278] that kilovolt electrons cause desorption of thermally labile organic molecules has been confirmed by the present investigations. Time-of-flight mass spectra were obtained for several organic samples and CsI. A comparison with mass spectra obtained from the same samples by means of the plasma desorption mass spectrometry is made. Ion yields were measured as a function of the electron energy. A possible desorption mechanism is proposed.

Gold clusters Aun with n ⩽ 5 and masses m ⩽ 985 u have been accelerated to MeV energies with the tandem accelerators at Orsay and Erlangen. Singly charged negative cluster ions were obtained from a conventional sputter ion source and accelerated between ground potential at the entrance of the accelerator and the terminal (in the middle) at several MV. In a gas channel positioned in the terminal they lose one or several electrons and become neutral or positively charged clusters, respectively. The ions are then accelerated towards the exit of the tandem accelerator. Identification of Au+n clusters is achieved by measuring the time-of-flight of the clusters.