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This is a brief review of some works on the models of atoms and molecules. The existence and absence of ground states are examined.

We are conducting various spectroscopic studies utilizing the characteristic properties of impurity atoms introduced into the superfluid helium (He II) environment. In He II, it is known that a vacuum region (atomic bubble) is formed around an impurity atom due to the repulsive force between an introduced atom and He atoms, and causes the Storks shift. The shift caused by a deformation of the bubble that follows the change in the electron orbit of the impurity atom, but there is no spectroscopic observation in time-domain experiment. In this study, we aim at the first observation of relaxation time by applying the time-correlated single photon counting method of photochemistry and measuring the time change of fluorescence wavelength. As the first step, we successfully observed the D1 emission of Rb atoms in He II by using ultrafast spectroscopy.

We are studying energy level structures of atoms by using laser spectroscopy. In particular, I aim at laser-induced fluorescence (LIF) observation experiments using rubidium-encapsulated gas cells to obtain hyperfine structure resolved spectra of rubidium atoms. In order to perform LIF observation, an excitation laser with high stability and sufficient wavelength scanning range is indispensable.In this study, I developed a wavelength control system of an external cavity laser diode (ECLD) system for LIF observation of Rb atoms. I have successfully observed LIF of Rb atoms using continuous wide range wavelength sweep of 80GHz.

Hyperfine structure energy splitting of atoms in superfluid helium (He II) is known to be slightly different from that in vacuum. We have been developing a pressure-variable cell for laser-RF/MW double resonance spectroscopy of Rb and Cs atoms in He II to measure the variation of hyperfine structure energy splitting with varied pressure to elucidate interaction of atoms with He II.In this study we aim at verification of detection system of laser-induced fluorescence (LIF) by photon counting method using photomultiplier tube (PMT), and performance evaluation of external cavity laser diode (ECLD) prepared as pumping source for Cs atoms as preliminary experiments. We here report detection of LIF from Cs atoms in gas cell and spin polarization using photon counting method towards double resonance experiments.

A laser processing technology is progressing in associate with a development of nanotechnology. A laser ablation in liquid is valuable for creating micro and nano particles. In particular, micro particles generated by laser ablation in superfluid helium are known to be in spherical shape. Among them, Zinc Oxide (ZnO) is one of the most promising materials for optoelectronics in UV region. ZnO microspheres generated in superfluid helium are utilized for optical resonators using Whispering Gallery Mode (WGM). It is because of the high refractive index of ZnO in UV region. We aim to study functionalities of micro particles generated in superfluid helium. The purpose of this study is generating and analyzing ZnO micro particles using laser ablation in liquid N_2 for the future experiment of laser ablation in superfluid helium and for investigating effect of liquid N_2 on micro particles. We successfully observed SEM images of micro particles and measured their sizes. From these results, we calculated frequencies of WGM.

Collinear laser spectroscopy enables us to systematically measure hyperfine structures and isotope shifts of atoms with a high precision and then determine charge radii and electromagnetic moments of their nuclei. We are developing a collinear laser spectroscopy setup towards applying this technique to slow RI beams provided from the SLOWRI facility in RIKEN. We choose Ba^+ ion as the test ion for evaluation of the apparatus, and assembled a 455nm ECLD (External Cavity Laser Diode) which produces a laser light resonant to the D2 line of a Ba^+ ion. The frequency of the ECLD was stabilized by using a feedback control from a high precision wavelength meter. We performed the spectroscopic experiment with the frequency-stabilized ECLD. We succeeded to measure hyperfine structures and isotope shifts for stable Ba isotope ions.

We have been developing a laser spectroscopy technique called OROCHI to study nuclear structure of low production yield unstable nuclei. In OROCHI, energetic ion beams generated at accelerator facilities are stopped in superfluid helium with high efficiency (～100%) and neutralized. Zeeman structure splitting of atoms is measured using laser-radio frequency double resonance method to determine their nuclear spins. We can also derive nuclear electromagnetic moments from the measurement of hyperfine structure splitting using laser-microwave double resonance method. In this study, we report two topics. One is the measurement of the resonance intensity dependence on a microwave antenna position using a Rb gas cell. The other is the estimation of the measurement time of the double resonance signal from a small number of atoms in super fluid helium using a fluorescence detection system.

The final goal of this study is to elucidate the nuclear structure by using collinear laser spectroscopy for the ion beam of unstable nuclei generated from an accelerator. In this study, we aimed to neutralize Rb ions with a neutralizer apparatus which utilizes an electron plasma, and tried collinear laser spectroscopy for the neutralized Rb atomic beams. In addition, we evaluated the charge transfer rate for Zr multiply charged ions using alkali gasses.

Recently, the atomic arrangement analysis of dopants in crystal using atomic resolution holography, such as photoelectron holography, X-ray fluorescence holography and neutron holography become possible. The equation for converting an atomic arrangement to an atomic resolution hologram is given. In order to obtain an atomic arrangement from a measured hologram, it is necessary to perform inverse conversion, which is an underdetermined system. L1 regression used for machine learning is effective to solve it. Taking photoelectron holography as an example, the principle of the atomic resolution holography, algorithm to a tree-dimensional atom image, and the analysis of atomic arrangement of the phosphorus dopant in diamond by photoelectron holography are shown.

The tunability of the frequency of a stabilized laser was accurately determined with a frequency marker. The marker was a Fabry-Perot optical cavity that consisted of two plane mirrors arranged in parallel. The intensity of the laser light transmitted through this marker was monitored while we continuously changed the stabilized laser frequency, and we determined the tunability of the stabilized laser on the basis of how many resonant peaks were observed. Previously, we determined the tunability of our stabilized laser to be more than 300 MHz using the spectrum at which atomic saturation occurs. However, it turned out that the precise tunability was 478.6 MHz with this technique.

A Rydberg exciton is a Coulomb-bound pair of an electron and a hole excited to a large principal quantum number n, analogous to a Rydberg atom. This highly excited state in solid potentially has exaggerated properties, such as a large Bohr radius, long-range interaction, and high sensitivity to environment, which are relevant to quantum technology applications. An oxide semiconductor Cu2O recently receives particular interest owing to the giant Rydberg excitons observed up to n = 25. In this article, we introduce our photoluminescence studies, which elucidated how these Rydberg excitons are generated, non-radiatively annihilated, and radiatively recombine when they are confined into mesoscopic dimensions.

The visualization of hydrogen distribution in materials is important to understand hydrogen embrittlement behavior. Neutron imaging experiment was carried out in order to visualize the distribution of solute hydrogen in an Al-10.1％Zn-1.2％Mg alloy and a pure palladium after hydrogen charging. Changes in the contrast of neutron transmission images caused by hydrogen were clearly observed in a palladium. In the wavelength range of 2-3 Å and 5-13.5 Å, the mean neutron transmission around the center of a hydrogen-charged palladium were 0.692 and 0.511, respectively. The hydrogen content in a palladium was estimated to be 10.8 mol％ from the measured neutron transmission. In this study, it has been demonstrated that hydrogen content can be analyzed even in non-monochromatic neutron imaging by considering the wavelength dependence of neutron intensity, and the effects of incoherent scattering and of Bragg-edge on transmission. On the other hand, hydrogen could not be observed from the neutron transmission image in Al-Zn-Mg alloys. This was due to the low hydrogen content, which was mass ppm level even after hydrogen charging, and statistical precision was not suffcient to discuss the amount of hydrogen of the mass ppm order.

The values of the internuclear distances and the dipole moments of 14 small molecules have been estimated by machine learning with only molecular orbital energies as the explanatory variables. We use four regression methods, partial least square (PLS), random forest (RF), Radial Basis Function Kernel Regularized Least Squares (krlsRadial), and Baysian Regularized Neural Networks (BRNN) and we report only BRNN results for the internuclear distances, and PLS results for the dipole moments. The coefficients of determination for the internulear distances and the dipole moments are 0.9318 and 0.7265, respectively. It has been proved that the internuclear distances and the dipole moments can be predicted by the molecular orbital energies only.

We are conducting spectroscopic study of atoms introduced by laser ablation of solid sample placed in liquid. In particular, we aim at observation of light called laser induced fluorescence (LIF) emitted when atoms in superfluid helium (He II) are excited with a laser and de-excited. When we irradiate a pulsed laser for laser ablation of sample in liquid, bubbles are generated by the evaporation of the surrounding liquid. It is important to know the behavior of these bubbles for the efficient introduction of atoms into liquid. In this study, laser ablation in liquid experiments was carried out using liquid nitrogen as a pilot experiment prior to using He II. We use the second pulsed laser as probe laser to detect scattered light caused by the surface of bubbles. The dynamics of bubble can be tracked by changing the time between two laser pulses. We observed the intensity change of the scattered light of the probe laser a few times with several 10 us intervals, which could be the consequence of the bubble formation and deformation.

We have been developing a laser spectroscopy technique called OROCHI to study nuclear structure of low production yield unstable nuclei. In OROCHI, the energetic ion beams generated at an accelerator are stopped in superfluid helium with high efficiency (～100%) and neutralized. Zeeman structure splitting of atoms is measured using laser-radio frequency double resonance method to determine their nuclear spins. We can also derive nuclear electromagnetic moments from the measurement of hyperfine structure splitting using laser-microwave double resonance method. It is also important to develop measurement method for various atomic species without using accelerators. For this purpose we introduce stable isotopes into superfluid helium by laser ablation method. We have so far successfully applied OROCHI to alkali atoms such as Rb and Cs. However, studies of atomic species other than alkalis are limited. In this study, we successfully introduced Ag atoms into superfluid helium using two-step laser sputtering by changing the wavelength of the second laser. As a result, we successfully measured the hyperfine structure splitting of Ag atoms.

We have been developing a laser spectroscopic method for atoms injected into superfluid helium (He II). We aim to measure hyperfine structure splitting which is caused by interaction between nuclei and valence electrons. So far, in the offline experiment, we succeeded in the measurement of hyperfine structure splitting of Rb. However, measurement accuracy and precision were not enough to discuss interaction between Rb and He atoms because of baseline fluctuation caused by instability of the number of atoms supplied by using laser ablation method. In this study, we developed a baseline correction system composed of electro-optic modulator and multi channel scaler, and performed baseline correction experiment by using this system for Rb in He II.

We have been developing a pressure variable cell system for laser spectroscopy of alkali-metal atoms immersed in superfluid helium (He II) to measure optical characteristics of atoms in varied He II pressure. We aim to measure Zeeman and hyperfine structure splittings of atoms immersed in He II by applying laser-radio-frequency (RF) / microwave (MW) double-resonance methods in various condition of helium. In general, temperature is dependent on pressure under standard vapor pressure, thus it is necessary to develop an internal cell to make it possible to vary pressure independently in He II and observe laser-induced fluorescence (LIF) emitted from atoms in this cell. In this study, we report two topics. One is the development of a system to vary pressure and temperature of He II where we observe LIF emitted from atoms in this system. The other is the development of laser-RF double-resonance measurement of atoms by laser ablation in the pressure variable cell.

The lithium isotope effect in ionic superconductors is numerically investigated. Using first-principles and kinetic Monte–Carlo simulations, the diffusion coefficients of 6Li and 7Li ions are calculated. Two important effects that cause the difference in the mobilities of lithium isotopes are also shown: the quantum effect, which decreases the activation barrier energy for lithium ion in a certain structure and increases the ratio of the diffusion coefficient of Li isotopes, as well as the correlation effect between 6Li and 7Li ions and vacancies. These results will assist in finding materials that exhibit large lithium isotope effect. The preferred chemical composition of lithium isotopes required to enhance the lithium isotope effect and the application of these isotopes as a separation membrane for the lithium ionic superconductors are discussed.

Introduction of hydrogen can significantly alter the physical properties of materials. However, conventional methods of hydrogen introduction are limited to a few materials and need very long time to introduce a large amount of hydrogen. We have focused on a low-temperature hydrogen ion beam irradiation, which is, in principle, applicable to any material of interest. In this study, we have developed a new low-temperature hydrogen ion beam apparatus for in situ physical property measurement, and low-temperature irradiation effects on ZnO thin films were investigated for the first time.

We reveal that an intense laser field deforms an inner valence orbital (10a') in the ethanol molecule. Using photoelectron-photoion coincidence momentum imaging, we measure the recoil-frame photoelectron angular distribution (RFPAD) for the CD2OH+ production channel of CH3CD2OH induced by a circularly polarized intense (I0 ≈ 8×1013 W/cm2) near-infrared (λ ≈ 795 nm) laser field. Ab initio simulations show that the orbital deformation depends strongly on the laser field direction, and that the measured RFPAD cannot be reproduced without taking the orbital deformation into account., XXXIst International Conference on Photonic, Electronic, and Atomic Collisions (ICPEAC2019)

To obtain a reference signal accurate enough for maintaining laser oscillation frequency, we stabilized the resonance frequency of a high-finesse transfer cavity whose finesse amounts to 313. We observed the derivative spectrum of the transmission one by modulating the cavity length and phase-sensitive detection and used this derivative signal as an error signal for controlling the cavity length. With the servo control, we successfully locked the resonance frequency of the high-finesse transfer cavity for 2 hours. Furthermore, the frequency stability was estimated to be 0.17 MHz when the signal bandwidth in the servo system corresponded to almost 160 Hz. This performance is sufficient to be used as a highly-versatile and stable reference signal for a light source in high-resolution spectroscopy of atoms.

This paper reports about the cooling of paraffin in horizontal cylindrical container. In this cooling process, the temperature change of paraffin in liquid and solid had made an interesting behaviors. We have analyzed this phenomenon using super-cooling and freezing point depression and explained reasonably and simulated successfully.

Propagation of higher order mode Lamb waves of 2 MHz in a glass plate is visualized using a strobe photoelastic system introducing sensitive tint visualization method. The birefringence from stresses causes the interference of color while the Lamb waves propagation. Time transition of ultrasonic waves propagation can be observed by varying the timing of strobe pulse light. A2 mode Lamb waves are selectively excited using oblique incidence by the wedge. Incidence angle was adjusted by the phase velocity calculated by the Rayleigh-Lamb frequency equation. Obtained bitmap image from the visualization system and CMOS camera are processed to enhance the contrast. Directions of applied forces were determined using image of static stresses. Lamb waves in the glass are clearly visualized with the polarity of sound pressure.

We are measuring hyperfine structure energies of atoms in superfluid helium using laser/microwave double resonance method. Further study of atomic structures under various pressure conditions is expected to provide more detailed information of interaction between impunity atoms and surrounding helium atoms. For thepurpose, we have developed a pressure variable cell that can be placed in superfluid helium environment as wellas the system to introduce atoms into the cell. We have constructed the cell, adopted the laser ablation method for the introduction of atoms and installed the laser-induced fluorescence observation system. It is shown that the above developed system satisfies the requirements for the experiment in the varied pressure conditions.Key Words : Laser spectroscopy, Superfluid helium, Laser ablation method

We aim to study the energy level structures of atomic ions in superfluid helium. These impurity ions areexpected to show interesting features due to the interaction between ions and surrounding helium atoms. Toestablish the method to introduce ions into superfluid helium, we have examined the effectiveness of the laserablation in liquids. A solid sample of barium is placed in a quartz cell filled with superfluid helium and ablatedby the second- and third-harmonic generations of a Nd:YAG laser. We have successfully observed fluorescencesignal from Ba ions produced by laser ablation in the observation region. Difference in the productionefficiencies of Ba ions by the wavelength of the ablation laser is discussed.Key Words : laser spectroscopy, laser ablation, barium ions, superfluid helium.

We stabilized the oscillation frequency of a laser diode by using the Zeeman effect of an atomic spectrum. We applied a magnetic field with a permanent magnet to rubidium atoms enclosed in a glass cell. Two circularly polarized (σ＋ and σ－) laser beams were entered into the cell to obtain the Zeeman-shifted, Doppler-broadened spectra. The error signal for controlling the laser frequency was generated with these spectra. As a result, the stability of the laser frequency reached 7.8 MHz. The tuning range was more than 250 MHz, which was determined from the saturated absorption signal. For a simpler experimental arrangement, we performed another frequency control experiment using the linearly polarized laser beam, where we detected both the blue- and the red-shifted Doppler-broadened spectra due to the Zeeman effect with a single incident laser beam. The resultant stability of the laser frequency was 12.9 MHz. Though the stability worsened, the tuning range was almost the same as the previous one. The oscillation frequencies of a variety of single-mode cw lasers should be controlled with a wider tuning range when our developed stabilization techniques are combined with a transfer cavity.

We have studied in detail the emission of superfluorescence at a wavelength of 469 nm (4p→3s) from helium ions created and excited using free-electron laser pulses from SACLA’s BL1. In earlier work we observed superfluorescence at visible wavelengths in neutral helium [1-5]. To observe superfluorescence from helium ions we used a wavelength of 24.3 nm, resonant with the He + 1s→4p transition and sufficiently short to ionise neutral helium atoms. The density of excited He + ions created by this sequential 2-photon absorption was sufficient to allow for the development of superfluoresence., 原子衝突学会第43回年会

This paper describes a laser optical tweezers (LOT) system, which was constructed by combining a diode laser with an optical microscope equipped with a long working distance objective lens. The system incorporates motor-driven beam steering optics which allows for positioning the trapping spot with micrometer resolution. The LOT system was applied to the manipulation of several particles, such as a polystyrene particle, a ceramic particle, a yeast cell. etc. The optical trapping forces and the optical rotation torque of the system were determined by the viscous drag forces and torque calculated using Stokes' law. The experimental results showed that trapping forces linearly increased with the laser power, and the forces generated were of the order of piconewtons (pN) when the laser power was about 10 mW. The rotation torque also linearly increased with the laser power and the observed increase in torque with power was approximately 10-19 Nm per mW. The values of the trapping forces and torque were compared to the momentum and angular momentum of the laser beam. It was shown that the LOT system developed here can be used in the manipulation of red blood cells and the rotation of a micro gear of 1μg in weight., 半導体レーザと長作動距離対物レンズの組み合わせからなる光ピンセットを開発し,その基礎特性を調べた.開発した光ピンセットは各種微粒子の捕捉,移動,回転ができることを確認した.トラップ力および回転トルクはレーザパワーに比例して増加し,レーザ出力10mWでトラップ力はpN,回転トルクはpN・mmオーダとなる.フォトンの運動量および角運動量と比較した結果,トラップ力はレーザの放射圧の約2.3%,回転トルクは円偏光レーザの全トルクの約25%に相当することがわかった.

Stark予想の精密化、一般化についての新しい理論を構築した。Rubin-Stark元の整性(integrality)に関して、そこに登場するイデアルの数論的意味を明らかにし、さらには同変玉河数予想が述べるゼータ元との間の関係を明らかにした。Stark元をゼータ関数のs=0での値だけでなく、任意の整数での値に対して定義し、精密化Stark予想をこれらの対象に対しても一般化した。また、一般化Stark元たちがp進族をなすことを発見した。古典的岩澤加群のFittingイデアルを完全に決定した。Brumer Stark予想と関連した岩澤加群のFittingイデアルの問題に完全な解答を得た。 We constructed a new theory on refinement and generalization of Stark conjecture. We discovered the arithmetic meaning of the ideal which appears in Rubin-Stark conjecture, and the relation between Rubin-Stark elements and zeta elements in equivariant Tamagawa number conjecture. We defined Stark elements to arbitrary integer points of zeta functions, and generalized the refined Stark conjecture to these generalized Stark elements. We found that these generalized elements form p-adic families. We determined the Fitting ideal of (non-modified) classical Iwasawa modules, and gave a complete answer to the problem on the Fitting ideal related to the Iwasawa theoretic version of Brumer Stark conjecture., 研究種目 : 基盤研究(A)(一般) 研究期間 : 2013～2017 課題番号 : 25247002 研究分野 : 整数論

According to a theoretical calculation, hydrogenated atomic vacancies in graphene were predicted to have a low energy barrier and little adsorption heat for additional hydrogen molecules. In this study, defects were introduced into epitaxial graphene by ion beam irradiation, and their chemical structure was investigated using XPS, Raman spectroscopy, and Elastic Recoil Detection Analysis (ERDA). Exposing defects-introduced graphene by ion-beam irradiation to hydrogen molecular gas and air results in hydrogen and oxygen-terminated defects, respectively. Evaluation of hydrogen amount of the surface by ERDA and temperature programmed desorption analysis suggests that the hydrogen diffusion into the plane of graphene with hydrogen terminated vacancies.

In hot plasma creation by heavy ion beam irradiation, K-shell ionization of target atoms is accompanied by outer-shell ionization. This process is called multipleionization. In the case that multipleionization by incident heavy ions are comparable to single ionization by plasma electrons, ionization degrees of target atoms are enhanced, giving misleading estimation of plasma temperature if the processes are not considered in the plasma diagnostics. In this study, population kinetics are solved under a collisional radiative equilibrium (CRE), and the plasma conditions where the multipleionization has a contribution are clarified.

"Femtosecond and nanosecond laser processing properties of organic thin film are evaluated by observation with laser microscope to study laser patterning technique for organic solar cell. Femtosecond laser processing quality is better and the required laser energy is lower in comparison with nanosecond laser one due to laser processing phenomena. In addition, using assist-gas is not good for micro processing of organic thin film. Because, the micro processing does not achieve in this case. For laser patterning quality, the interaction between laser and plasma and the stage speed also relates for processing quality."

We developed a subtraction circuit to measure the saturation spectra of rubidium atoms without using a lock-in amplifier. An instrumentation amplifier (IA), which is a type of differential amplifier, was used. We designed our IA to have an adjustable gain of 4.3 - 21 to obtain saturation spectra with a good signal-to-noise ratio. With our IA, we tried to deduce the saturation spectrum by subtracting the Doppler signal from the transmission spectrum of rubidium atoms enclosed in a glass cell. As a result, the obtained saturation spectra have six peaks originating from the atomic and cross-over resonances, and their line widths are 11.2 MHz. This number of peaks is the same as that detected with a lock-in amplifier, and the line width is smaller than that detected with a lock-in amplifier. Therefore, we confirmed that our IA has equivalent performance to a lock-in amplifier for measuring the saturation spectrum of atoms.

We have simulated the reflection of long wavelength laser pulses with varying intensity off of plasma waves (relativistic mirrors) generated by a strong driver laser pulse. The laser pulses have been found to reflect off both non-breaking and breaking plasma waves. As the intensity of the laser pulse increases a broad range of wavelengths are generated with less clear indications of structures in the frequency spectrum., レーザープラズマ科学のための最先端シミュレーションコードの共同開発・共用に関する研究会

Low-lying electric dipole (E1) and magnetic dipole (M1) excitations are fundamental modes of atomic nuclei. The observation of the E1 and M1 transitions provides information on the collective and single-particle modes of nuclear excitation such as pygmy E1 resonance (PDR) and spin-flip M1 resonance. We will talk about the results of recent NRF measurements on Fe, Pb, and Ta isotopes., 40th ASRC International Workshop "Experimental and Theoretical Advances in Fission and Heavy Nuclei "

The OODR mass spectroscopy is applied to investigate dynamical properties of Xe**Kr in high Rydberg states. It is found that two dissociation pathways producing both the Xe** and Kr** fragments compete, where the ion core of high Rydberg molecule switches. It is revealed that ion-core switching (ICS) occurs because of the interaction between bound potentials of high Rydberg states Xe**Kr and a repulsive potential of XeKr**. Moreover, the observed variation in ICS ratio is explained by the population transfer from high Rydberg states of Xe**Kr of the A ion core to those of the X ion-core., 第10回分子科学討論会

In hot plasma creation by heavy-ion-beam irradiation, K-shell ionization of target atoms is accompanied by outer-shell ionization by ion impacts. This process is called multipleionization. In the case that multipleionization by incident heavy ions is comparable to single ionization by plasma electrons, an ionization degree of target atoms is enhanced, giving misleading estimation of plasma temperature if the processes are not considered in plasma diagnostics. In this study, Kα spectra are calculated with and without the multipleionization by solving population kinetics under collisional radiative equilibrium (CRE), and plasma conditions where the multipleionization has a large contribution are clarified.

A low cost and stable terahertz wave source using a laser chaos is developed. Optical spectra of the laser chaos are broad. In order to oscillate the laser chaos, an optical delayed feedback is introduced using an external mirror. Thus, the optical spectrum is spread about 70 times compared with that the C.W. steady semiconductor laser and the frequency interval between longitudinal modes is about 50 GHz. Optical beats occurs between semiconductor laser's longitudinal modes and these frequency intervals a 50 GHz. Therefore, the laser chaos is important to generate the stable and wide range terahertz wave. Mixing the He-Ne laser with the semiconductor laser chaos system, it's possible to generate THz waves up to 0.864 THz.

We used a novel approach to stabilize the 780-nm laser frequency by using the cross-over resonance of Rb atoms. The signal intensity of the cross-over resonance is generally larger than that of the resonance between atomic energy levels. Therefore, laser frequency control using the cross-over resonance is expected to achieve better stabilization and a wider tuning range, compared with the conventional one. The observed cross-over signal obtained from the saturation absorption spectrum has a line width of 12 MHz, which is attributed to the natural line width of atomic transition and the residual Doppler broadening due to the misalignment of the counter-propagating laser beams. As a result of our frequency control, the stability was improved to approximately 0.4 MHz for 100 s, though the free-running laser drifted almost 54 MHz. The resultant laser is applicable as a light source to be used in the high-resolution spectroscopy of Rb atoms.

Neutrino-induced reactions on per-existing isotopes in supernova explosions can produce rare isotopes such as 92Nb, 138La, 180Ta. The abundances of these isotopes depend on the temperatures of the six types of neutrinos. We discuss nucleosynthses by the neutrino-process and its temperature dependence., 2nd NAOJ-ECT* Workshop on Many Riddles About Core-Collapse Supernovae: 1 Bethe and Beyond

Bose-Einstein condensation was realized in dilute gases of Alkali metals and Hydrogen atoms. The scattering length can take a positive or negative value by a subtle change of parameters even if the atomic interaction is always the attractive Van der Waals potential. The scattering length determines the effective interaction in BECs, i.e., the effective interaction is attractive (repulsive) when the scattering length is negative (positive). In this paper, we propose a model system in which the atomic interaction potential obeys a repulsive power law in the long range, and obtain the expression of the scattering length of this model analytically.

Vaporization of helium and argon mixture is studied by molecular dynamics simulations. The numbers of molecules in the basic cell are 128 for both species. The ensemble is NTP. The two liquid phases are observed at low temperatures. At intermediate temperatures, the vapor phase with main component of helium and liquid phase of argon are found. Finally, the evaporation is completed, where there is the gaseous mixture of helium and argon. These features are studied by the average potential energy and volume as functions of temperature.

The gas pressure dependence of breakdown voltages of a micro-hollow cathode discharge is investigated.Experiments were carried out on a cylindrical hollow cathode,0.5 mm in diameter and 3 mm in depth in wide range of gas pressure of helium and its mixtures.Calculated Paschen curve based on Townsend theory were compared with the experimental results.The influences of admixed hydrogen and water vapor on the breakdown voltage ware considered by the modification of the ionization coefficient.The ionization by Penning collision between a hydrogen molecule and a helium excited atom is included by the addition of excitation coefficient to the ionization corefficient.The electron attachment with a water vapor is treated as the decrease of electrons contributive to ionization and the decrease of positive ions to the cathode surface contributive to the secondary electron emission.

This paper discusses the differences between two-dimensional models and three-dimensional models of cooling channel layout designs in a plastic injection molding die. To identify the differences, two kinds of three-dimensional numerical models are designed by the design method of cooling channel layout proposed in our previous research. The results show that, when the cooling channel layout is required so as to rapidly cool down and make temperature distribution of the plastic materials uniform, distinct cooling channel layouts are obtained because of different flow rates of coolant in the cooling channel between them. And also, it is shown that the distance between the cooling channel and cavity in the die is an effective factor to control the temperature distribution of plastic materials. From this result, the cooling channel layout design is implemented in two steps. At first, the distance between the cooling channel and the cavity is decided. The result of the first step is utilized as the initial design of the next step. In the second step, the length of cooling channel is designed. In addition, it is found that the surface area of cooling channel is important to control the temperature distribution of the plastic materials.

Possibilities of the future society with hydrogen utilization have been discussed as one of the advanced technologies for the improvement of the energy and environmental problems in recent decades. In order to go on generating the effective energies by oxidizing the hydrogen with a fuel cell etc., it is necessary to establish the total system for producing, transporting, storing and transferring the hydrogen safely and stably. At that time, it can also be essential to use the hydrogen as a liquefied gas as well as a compressed gas. In this study, the operation of a superconducting level sensor for liquid hydrogen with a magnesium-diboride wire is numerically simulated on the basis of experimental results carried out previously. The time evolution of temperature distribution along the wire is calculated with a heat balance equation including the cooling effects of liquid hydrogen and its vaporized gas. The influences of the wire size and material properties on minimum propagating current and power consumption in the gaseous hydrogen are evaluated toward the optimal design of the level sensor.

We experimentally investigate the synchronization of bandwidth-enhanced chaos in a semiconductor laser (drive laser) that is subject to optical injection from another chaotic semiconductor laser (injection laser) with optical feedback. Effective bandwidth enhancement is achieved over 12 GHz outside the injection locking range. The bandwidth-enhanced chaotic signal of the drive laser is injected into a third semiconductor laser (response laser) for synchronization. Synchronization of chaos with a bandwidth greater than 12 GHz is observed between the drive and response lasers, under the injection locking condition. High-quality chaos synchronization is observed within the injection locking range between the drive and response lasers.

Space solar power station needs an energetic and efficient laser as the energy transfer device from a broadband solar light to a coherent laser light. The concept of active-mirror amplifier with transparent Nd/Cr:YAG (Yttrium Aluminum Garnet) ceramics is proposed under consideration how to convert a wide spectrum of sun light to a monochromatic laser light. New ceramic material pumped by an arc-metal-halide lamp has been implemented experimentally as a fundamental prototype for the space solar power station. CW (Continuous Wave) laser light generated in a LD (Laser Dye)-pumped 1,064-nm Nd:YAG rod laser oscillator was amplified so that a spatial mode of laser output has been improved to Gaussian mode. The saturated amplification of output laser power was observed at around 40 W/sq cm in output power density when the diameter of input laser profile was 18 mm. The maximum output laser power obtained was up to 180 W (about 60 W/sq cm) with keeping spatial beam quality when Nd:YAG ceramics doped Cr ions density of 3 percent was used., 資料番号: AA0063965018

We experimentally observe synchronization of two semiconductor lasers commonly driven by a chaotic semiconductor laser subject to optical feedback. Under condition that the relaxation oscillation frequency is matched between the two response lasers, but mismatched between the drive and the two response lasers, we show that it is possible to observe strongly correlated synchronization between the two response lasers even when the correlation between the drive and response lasers is low. We also introduce separate optical feedback to the two response lasers. The maximum correlation between the two response lasers is obtained when the phase of the feedback light is matched between the two response lasers, while the minimum correlation is observed when the difference in the optical phase is π.

We developed a compact laser electron source which can be used as an X-ray source for nondestructive diagnosis instead of radio isotopes. High energy electrons were generated by an ultrashort laser pulse focused on a thin tape target. The laser energy was only 15 mJ. Pulse duration and beam diameter of the laser beam were 140 fs and 10 mm, respectively. We got over 1 MeV energetic electrons with this compact laser electron source.

Numerical simulation of hydrogen dispersion in a partially open space is performed in this paper. The transient behavior of hydrogen and the process of hydrogen accumulation in the space are discussed. Also, the effects of changing vent position and condition on the distribution of hydrogen concentration are shown. Based on the results, conditions for preventing dispersion and accumulation of hydrogen in the space are discussed.