We report emission properties of single-atom tips, noble electron sources terminated with a single atom. The repairing function of the sources, which had been already demonstrated by using field ion microscope [Fu, et al. Phys. Rev. B 64, 113401 (2001)], was confirmed by using field emission microscopy, and in addition, the demountable character was demonstrated repeatedly. The brightness of the collimated beam emitted from the single-atom tips was estimated to be an order of 10 10 A/cm 2 /str. (E ∼ 2 keV), which is two orders of magnitude higher than those of the conventional field emission sources. There appeared an extra shoulder in the energy spectra, which is strongly correlated with a single-atom ended structure. The fluctuation of the emission current exhibited stepand spike-like noises, which were typical features of nano-electron sources. The single-atom sources are promising candidates of the electron sources in high-performance electron-beam instruments.

We investigate the ratio of double to single ionization of He in an intense laser field based on the rescattering model. Folding the rescattering energy spectra with the electron impact inelastic cross sections, we obtain the probability of double ionization due to the nonsequential ionization process. Our results are in reasonable agreement with the experiment [Walker et al., Phys. Rev. Lett. 73, 1227(1994]. Furthermore, we investigate the physical insights of the nonsequential double ionization by analyzing the rescattering energy spectra at different intensities and the contributions from individual returns. This study confirms the reliability of the rescattering energy spectra obtained from ab initio calculations. The rescattering information can be used to analyze many other dynamical processes in intense laser-matter interactions, such as molecular imaging.

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Abstract. The isoscalar giant dipole resonnace (ISGDR) has been investigated in 208 Pb using inelastic scattering of 400 MeV α particles at extremely forward angles, including 0 • . Using the superior capabilities of the Grand Raiden spectrometer, it has been possible to obtain inelastic spectra devoid of any "instrumental" background. The ISGDR strength distribution has been extracted from a multipole-decomposition of the observed spectra. The implications of these results on the experimental value of nuclear incompressibility are discussed.Nuclear Incompressibility is a crucial component of the nuclear equation of state and, as such, has very important bearing on diverse nuclear and astrophysical phenomena: for example, strength of supernova collapse, the emission of neutrinos in supernova explosions, and collective flow in medium-and high-energy heavy-ion collisions. The only direct experimental measurement of nuclear incompressibility is possible via the compressional-mode giant resonances in nuclei. Of the two important comprssional modes, the isoscalar giant monopole resonance (GMR) is the better known and has been studied now for more than 20 years. The other mode, the isoscalar giant dipole resonance (ISGDR), is an exotic oscillation-to first order, isoscalar dipole mode represents simply the motion of the centerof-mass which, in itself, cannot lead to any nuclear excitation-which has remained somewhat elusive, even though initial (although inconclusive) evidence for the mode was reported as long ago as the early 80's.The ISGDR can be thought of a hydrodynamic density oscillation in which the volume of the nucleus remains constant and a compressional wave-akin to a sound wave-traverses back and forth through the nucleus. The mode has generally been referred to as the "squeezing mode" in analogy with the mnemonic "breathing mode" for the GMR. A general description of this mode, along with the relevant transition densities and sum-rules, has been provided in Refs. [1,2]. The energy of this resonance is related to the nuclear incompressibilty via the scaling relation:where K A is the incompressibility of the nucleus, m is the nucleon mass, and ε F is the Fermi energy [3]. As mentioned above, indications of the ISGDR were reported as early as the beginning of the 1980's. However, the first conclusive evidence for this mode, based on the differences in angular distribution of the ISGDR from that of the nearby high-energy octupole resonance (HEOR), was provided by Davis et al. [4], who demonstrated that in inelastic scattering of 200 MeV α's at angles near 0 • , the giant resonance "bump" at 3hω excitation energy could be separated into two components, with the higher-energy component corresponding to the ISGDR. Further evidence for