Search

We have been developing a laser spectroscopic method named OROCHI for the study of the nuclear structure of low-yield unstable nuclei produced by accelerators. Spin-polarized states are generated for RI atoms stopped in superfluid helium by optical pumping, and Zeeman level splitting and hyperfine structure splitting are measured by using the laser-radio frequency / microwave double resonance method. When atoms are introduced into superfluid helium, the absorption and emission wavelengths of the atoms are different. We take the advantage of the intriguing spectroscopic environment of superfluid helium. We aim to improve the efficiency of LIF(Laser Induced Fluorescence) detection to measure the unstable ^84Rb hyperfine structure splitting in superfluid helium at accelerator beamlines. For this purpose, we enlarged the intersection area between an excitation laser and an accelerated beam. We evaluated the effect of this modification.

We have been developing a laser spectroscopic technique called OROCHI to study nuclear structure of low production yield unstable atom. In OROCHI, the energetic beams generated at an accelerator are stopped in superfluid helium (He II) with high efficiency (～100%). This method enables measurement of Zeeman level to determine the nuclear spins and hyperfine structure level to determine nuclear electromagnetic moments using laser radio wave/microwave double resonance method.In this study, we focused on the effect of the external magnetic field on the atoms, which is one of the causes limiting the accuracy of the measurement. By introducing an external magnetic field correction coil, we aim to measure the hyperfine structure splitting of unstable ^84Rb atoms with high precision that enables the derivation of hyperfine anomaly in the future.

We have been developing a laser spectroscopy method for atoms introduced into superfluid helium (He II). We generate spin polarization by optical pumping of atoms and perform laser-radiofrequency and laser-microwave (MW) double resonance. This method enables us to determine the nuclear spins and electromagnetic moments through measurements of Zeeman splitting and hyperfine structure (HFS) splitting. Moreover, because HFS splitting energies in He II shift slightly from those in vacuum, we expect the phenomena lead us to study the interaction between He Ⅱ and atoms. We have so far successfully measured HFSs of alkali atoms such as stable ^85,87Rb and ^133Cs in He II. Currently, we are attempting to apply this method to group 11 atoms to investigate whether a similar difference appears in atoms other than alkalis. We are now trying to apply this technique to Ag atoms.In this study, we introduced a new pulsed laser with repetition of 20 kHz for optical pumping of Ag atoms and succeeded in obtaining laser-RF double resonance spectra. In addition, by obtaining a laser-MW double resonance spectrum using a Rb gas cell, we evaluated the accuracy and precision of MW frequencies when different MW sweep methods were used.

We have developing a laser spectroscopy method called OROCHI to study nuclear structure of low production yield atoms with unstable nuclei. In OROCHI, the ion beams generated at an accelerator are stopped in superfluid helium (He II) with high efficiency (~100%). This method enables us to measures Zeeman level to determine the nuclear spins and hyperfine structure level to determine nuclear electromagnetic moments using laser radio wave/microwave double resonance method. We have applied this method to highly energetic ^84Rb beams generated at HIMAC SB2 beamline. I here report the successful detection of laser-induced fluorescence from ^84Rb atoms stopped in He II.

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 under the circumstance of He II. However, it has been difficult to realize measurement with sufficiently high precision due to the fluctuation of the number of observed photons when we use two-step laser sputtering method to supply atoms into He II. To overcome this difficulty, a baseline correction system to cancel the fluctuation of the number of atoms was developed. In this study, we performed an RF double resonance experiment for Rb atoms injected into He II using the baseline correction system. And we evaluated the precision of the magnetic field strength applied to the atoms which will be utilized for the measurement of the hyperfine structure.

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.

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.

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.

Volatile organic compounds (VOCs) emitted from Akamatsu (Pinus densiflora) or Japanese red pine, the predominant conifer species found in Japan, were measured by gas chromatography with flame ionization detection (GC-FID). Eleven chromatographic peaks were obtained and assigned by standard samples except the biggest peak called X1. Based on various considerations, X1 was assigned as the peak of β-phellandrene. The total OH reactivity was also measured by a laser flash pump-probe technique at the same time as the GC analysis. The experiments were performed under a daily cycle simulated by controlling temperature and light intensity. A comparison between the expected OH reactivity calculated from the GC measurements and the measured OH reactivity revealed the existence of undetermined VOCs accounting for about 40% of the total OH reactivity. The unaccounted- for reactivity did not show any positive correlation with predominant monoterpenes detected from Akamatsu., 我国の優勢樹種であるアカマツから放出されるVOC濃度をGC-FIDにより測定した。11のピークのうちの未同定であったX1をβ-phellandreneと同定した。VOC測定と同時にレーザー分光法による総OH反応性を測定した。温度および光強度を制御して日サイクルを模擬的に作り出しVOCおよびOH反応性を測定した。個々のVOC測定から導かれる総OH反応性の計算値とレーザーにより実測される値の比較を行った。その結果、４割の未知VOCの存在が明らかとなった。未知VOCは観測されたいずれのモノテルペン類とも相関が低かった。, 地球環境学堂 大気環境科学

Laser spectroscopic study has been carried out for host-guest encapsulation complexes formed in supersonic jets and electrospray ionization cold 22 ion trap. The examined hosts include benzene-substituted 18-crown-6-ethers and calix[4]arene, and for the guest species rare gas atoms, neutral molecules and alkali metal cations have been chosen. Various laser spectroscopic methods are applied: for the neutral complexes the electronic spectra are observed by laserinduced fluorescence (LIF), mass-selected resonance enhanced multiphoton ionization (REMPI) and ultravioletultraviolet hole-burning (UV-UV HB) spectroscopy. The vibrational spectra are observed by infrared-ultraviolet double resonance (IR-UV DR) and fragment detected infrared photodissociation (IRPD) spectroscopy. For the ionic complexes, ultraviolet photodissociation (UVPD) and IR-UV DR spectroscopy has been applied. The obtained results are analyzed by density functional theory and first principles electronic structure calculations. We discuss how the host molecule changes its conformation or which conformer is preferred for forming stable encapsulation complex as well as the key interactions, leading to the molecular recognition.

Laser spectroscopic study has been carried out for host-guest encapsulation complexes formed in supersonic jets and electrospray ionization cold 22 ion trap. The examined hosts include benzene-substituted 18-crown-6-ethers and calix[4]arene, and for the guest species rare gas atoms, neutral molecules and alkali metal cations have been chosen. Various laser spectroscopic methods are applied: for the neutral complexes the electronic spectra are observed by laserinduced fluorescence (LIF), mass-selected resonance enhanced multiphoton ionization (REMPI) and ultravioletultraviolet hole-burning (UV-UV HB) spectroscopy. The vibrational spectra are observed by infrared-ultraviolet double resonance (IR-UV DR) and fragment detected infrared photodissociation (IRPD) spectroscopy. For the ionic complexes, ultraviolet photodissociation (UVPD) and IR-UV DR spectroscopy has been applied. The obtained results are analyzed by density functional theory and first principles electronic structure calculations. We discuss how the host molecule changes its conformation or which conformer is preferred for forming stable encapsulation complex as well as the key interactions, leading to the molecular recognition.