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The gas cluster ion beam (GCIB) is a valuable tool for surface analysis, providing new 3D mass analysis equipment possibilities. The main feature of the GCIB is that many particles are involved during the collision of the cluster ion beam with a sample surface. Studying the characteristics of the GCIB is essential for improving the performance of the analysis equipment. We evaluated the efficiency of the GCIB using a mixed-gas of Ar and CO2 as a primary ion beam for time-of-flight secondary ion mass spectrometry. We measured the characteristic factors and composition of the cluster ion beam depending on the mole fraction ratio of CO2/Ar. We measured that the CO2 composition of the output cluster ion beam rapidly increases to over 95% when the mole fraction ratio of CO2 increases by more than 10% in the injected mixed gas. Nevertheless, the optimal ratio of the CO2/Ar mole fraction (%) to increase the secondary ion efficiency was 96% CO2, which more than doubled the secondary ion efficiency over that of pure Ar clusters. The beam spot size began rapidly decreasing from 95% CO2, and it was reduced by up to 0.67 times at 100% CO2. According to the mixed-gas ratio, the sputtering yield of the Si wafer was 8 times lower than that of pure Ar clusters.

When an insulator sample is analyzed via time-of-flight secondary ion mass spectrometry (ToF-SIMS), charges accumulate on the sample surface due to the primary ion beam. These local surface charges and surface potentials cause many problems during analysis. A Kelvin probe was used to measure the surface potentials of the insulator sample. The surface potential induced on the surface of the sample and its temporal change was measured following the irradiation of the gas cluster ion beam. It was confirmed that the estimated surface potential value is affected by the high vacuum gauge, and there is an inflow of charges that possess polarities opposite to that of the surface potential. The amount of current flowing from the high vacuum gauge was calculated using the surface potential data that was measured. The amount of charge flowing onto the surface of the insulator was varied from several tens of fA to several fA, which was depended on its vacuum degree and position of high vacuum ion gauge. Additionally, neutralization of surface charges by the neutral gas effect was also weakly observed. This leaked current from the high vacuum gauges is likely to have a small but lasting impact on the ToF-SIMS insulator analysis.

The CD spectroscopy of a chiral compound in solution yields an average CD value derived from all of the conformations of a chiral molecule. By contrast, CD spectroscopy of cold chiral molecules in the gas phase distinguishes specific conformers of a chiral molecule, but the weak CD effect has limited the practical application of this technique. Reported herein is the first resonant two-photon ionization CD spectra of ephedrines in a supersonic jet using circularly polarized laser pulses, which were generated by synchronizing the oscillation of the photoelastic modulator with the laser firing. The spectra exhibited well-resolved CD bands which were specific for the conformations and vibrational modes of each enantiomer. The CD signs and magnitudes of the jet-cooled chiral molecules were very sensitive to their conformations and thus offered crucial information for determining the three-dimensional structures of chiral species, as conducted in combination with quantum chemical calculations.