Tsutomu Watanabe

Theoretical investigation of the point-spread function given by super-resolving fluorescence microscopy using two-color fluorescence dip spectroscopy

The profile of the point spread function (PSF) in superresolution microscopy is studied theoretically. The fluorescence spot profile (i.e., the PSF) is determined by the focused beam patterns of the applied two-color lasers and the optical properties of the fluorescence-depletion process induced by the lasers (the pump and erase beams). In this study, the fluorescence-depletion process for the sample molecule is analyzed using a rate equation for a three-state model. Based on this result, we calculate the PSF for the case where the erase beam is modeled by a first-order Bessel function. In the case of an erase beam with a large photon flux, the obtained PSF has a Lorentzian-like shape, which seldom appears in traditional microscopy. In this work, we also investigated a possible relationship between the PSF and other parameters in the fluorescence-depletion process.

Photometric study of new southern SU UMa-type dwarf novae and candidates: V877 Ara, KK Tel and PU CMa

We photometrically observed the three dwarf novae V877 Ara, KK Tel and PU CMa. We discovered the undisputed presence of superhumps in V877 Ara and KK Tel, with mean periods of 0.084 11(2) and 0.088 08(3) d, respectively. Both V877 Ara and KK Tel are confirmed to belong to long-period SU UMa-type dwarf novae. In V877 Ara, we found a large decrease of the superhump period ( ˙ P/P =− 14.5 ± 2.1 × 10 −5 ). There is evidence that the period of KK Tel decreased at a similar or a more exceptional rate. Coupled with the past studies of superhump period changes, these findings suggest that a previously neglected diversity of phenomena is present in long-period SU UMa-type dwarf novae. The present discovery of a diversity in long-period SU UMa-type systems would become an additional step towards a full understanding of the dwarf nova phenomenon. PU CMa is shown to be an excellent candidate for an SU UMa-type dwarf nova. We examined the outburst properties of these dwarf novae, and derived characteristic outburst recurrence times. Combined with the recently published measurement of the orbital period of PU CMa, we propose that PU CMa is the first object filling the gap between the extreme WZ Sge-type and ER UMa-type stars.

Study of x‐ray microscopy using ultraviolet and x‐ray double‐resonance absorption

Yoshinori IketakiResearch Development Corporation ofJapan (JRDC)‘‘Light and Material’’ PRESTO2-45-13 Honcho, Nakano-kuTokyo 164, JapanandOlympus Optical Co., Ltd.T. Morokuma Research Laboratory2-3, Kuboyama-cho, Hachioji-shiTokyo 192, JapanTsutomu WatanabeInternational Christian UniversityDepartment of Physics3-10-1 Ohsawa, Mitaka-shiTokyo 181, JapanE-mail: tsutomu@icu.ac.jpAbstract. The UV-and-x-ray double-resonance absorption process in 1mm tryptophan grains was studied. The excited molecular density can beobtained by the use of a three-state model for UV absorption. The de-pendence of the x-ray transmittance on the UV-laser photon flux usingwas investigated using the x-ray absorption cross sections obtained by acalculation based on the atomic Hartree-Slater method. It was found thatx-ray absorption is increased markedly by the use of a 5-ns UV pulsewith a peak photon flux of ;10

Hard x‐ray interaction with materials

Based on the analyses of microprocesses involved in the interaction of synchrotron radiation with materials, we have developed a simulation method to calculate heat energy distribution when the synchrotron radiation goes through insert devices (filters, mirrors, or monochromators). The absorbed x-ray energy may be taken away from materials when some scattered photon and photoelectron escape from material. We have calculated the percentage of the absorbed energy taken away by the escaped photons and photoelectrons for C, Be, and Al, these elements being very important as filter materials, and for Si which is significant as a monochromator material.

Mechanisms of giant resonance in 4d photoionization of Eu

We have studied the mechanisms of giant resonance in 4d photoionization of Eu atoms by density functional theory with the optimized effective potential and self-interaction correction method. The dynamic electron correlation is taken into account by the linear density response method. Our calculated photoionization cross sections in the giant resonance region are in good agreement with experimental measurements. Since Eu is a highly spin polarized system, by decomposing the contribution of 4d electrons in spin-up and spin-down states, we clearly identified that the strong asymmetry line profile of the giant resonance is due to a broad resonance of 4d spin-down electrons interaction with a sharp resonance of 4d spin-up electrons.

Heat‐energy deposition in x‐ray interaction with materials application to Si and Be

Based on the analysis of the micro‐processes due to the interaction of synchrotron radiation with materials, we have developed a theoretical method to calculate the heat energy deposited when synchrotron radiation passes through insert devices (filters, mirrors or monochromators). The micro‐processes are photoionization, Compton scattering, Rayleigh scattering, electron elastic and inelastic collisions, electron Bremsstrahlung scattering and the Auger process. The energy of x rays is converted into the electrons’ kinetic energy and atomic excitation energy by photoionization and Compton scattering. High‐energy photoelectrons slow down mainly through inelastic collisions with the atoms in materials. The energy deposition in a material is simulated according to the x‐ray atom interaction cross sections and photoelectron‐atom collision cross sections. The results of a calculation for x rays traversing Si and Be plates of 1.0 cm in thickness are presented and discussed as one typical example concerning import...

Green's function for multielectron ions and its application to radiative recombination involving dielectronic recombinations

We propose a general method to calculate the full Greens function of multielectron atomic ions. The key point exists in the usage of L{sup 2} integrable functions as a complete basis set in a finite region together with an optical potential to guaranty the outgoing scattering boundary condition. In such a way, the cumbersome procedure of adjusting boundary conditions in solving the differential Schroedinger equation is avoided. To show the validity of the method, we studied the radiative recombination involving dielectronic recombinations of Be-like Hg (Z=80) ions. The radiative damping effect is taken into account naturally in the present method. The calculated results reproduce well the asymmetric line profile observed in the experiments.

Potential-energy curves of core-excited NO molecules

Using an ab initio configuration interaction approach based on the Hartree-Fock method, the electronic energy levels of K-shell core-vacant NO molecules have been calculated as a function of the internuclear distance. The calculation included many outer-shell excited states of the inner-shell vacant NO. The vacant states are either in the K-orbital of the N atom or the O atom. The results of this calculation were compared with the spectroscopic data obtained using synchrotron radiation, and they were found to be in agreement to within 1-2 eV. Using these present results, we look at the possible x-ray and UV double-resonance absorption processes by NO molecules.

Optical properties of carbon compounds near carbon K-edge and their application to x-ray multilayers

In order to investigate the technical feasibility of X-ray optical devises in the XANES energy region, we used typical carbon compounds with (pi) * molecular orbitals i.e. C60, C70, carbon nanotube and graphite. Their real and imaginary parts of the optical constants were studied. In this study, using XANES observation spectrum data and calculations by the Hartree-Slater method, the atomic-scattering factors of compounds near carbon K-edge region were obtained. It was found that outstanding anomalous dispersions are observed in the near carbon K-edge region; and it was also found that the compounds have peculiar and complicated optical properties due to the chemical-bond structures. Furthermore, based on the obtained results, we designed a metal/graphite normal-incident X-ray multilayer in the region and also considered its application to an X-ray microscopy.

X‐ray microscopy using the photoexcitation to unoccupied π*‐character molecular orbits

We studied the possibility of soft x‐ray microscopy using unoccupied π*‐character molecular orbits of bases in DNA and RNA. We estimated the photoabsorption cross section of benzene molecule using the atomic base model. Discussion is extended to the case of nuclear acid bases caused by excitation of the 1s electron to the π* orbit under assumption of the similar electronic transition with the benzene case and found that for the photon energy used in this study it is three times larger than that for the photoionization of the 1s electron at the water window region. We concluded that an image of DNA or RNA in wet biological cells may be observed with good contrast using this proposed method.