A new reflectron time-of-flight mass spectrometer for surface analysis has been developed that incorporates a Schwarzschild all-reflecting microscope. The instrument is configured for secondary ion mass spectrometry and secondary neutral mass spectrometry using either ion beam bombardment or laser ablation for sample atomization. The sample viewing and imaging system of this instrument enables in situ laser microanalysis with a lateral resolution below 1 μm. The major advantages of using a Schwarzschild objective include good lateral resolution, easy design, low cost, complete achromatism, and both viewing the sample and extracting secondary or photoions normal to its surface. The instrument has a mass resolution of m/Δm≥2000 and is capable of measuring elemental and isotopic compositions at trace levels using resonance ionization. The isotopic ratios of trace concentrations of Ti in μm size SiC grains separated from meteorites were measured. The extremely low ablation laser power used in the above experiment points to the possibility of using low-cost laser systems for laser microprobe applications.

We present experimental and theoretical differential cross sections for the fine structure changing process Ar + O(3P2)→Ar + O(3Pjmj) with (j,mj)=(1,1), (1,0), and (0,0). The measured cross sections refer to a collision energy of 3.2 kcal/mol, and were obtained from Doppler line shapes associated with (2+1) resonance-enhanced multiphoton ionization of O(3Pjmj) after scattering in a crossed-beam apparatus. The theoretical results are based on 3Σ− and 3Π potential curves obtained from high quality ab initio calculations, and on quantum coupled-channel calculations. The calculated differential cross sections show strong Stuckelberg oscillations, with similar magnitudes and phases for all three final states. With slight adjustment (0.03 Å) of the hard wall on the 3Σ− curve, the calculated angular distributions match up well with the corresponding experimental results, much better than is found using previously derived empirical potentials. At the same time, the integral total cross sections obtained from the ab initio measurements are in satisfactory agreement with previous measurements.

Secondary neutral and secondary ion cluster yields were measured during the sputtering of a polycrystalline indium surface by normally incident-4keV Ar+ ions. In the secondary neutral mass spectra, indium clusters as large as In32were observed. In the secondary ion mass spectra, indium clusters up to Ini_8were recorded. Cluster yields obtained from both the neutral and ion channel exhibited a power law dependence on the number of constituent atoms, n, in the cluster, with the exponents measured to be-5.6 and-41, respectively. An abundance drop was observed at n=8, 15, and 16 in both the neutral and ion yield distributions suggesting that the stability of the ion (either secondary ion or photoion) plays a significant role in the z observed distributions. In addition, our experiments suggest that unimolecular decomposition of the neutral cluster may also plays an important role in the measured yield distributions.

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