Yoshiki Moriwaki

Ab initio study on vibrational dipole moments of XH+ molecular ions: X = 24Mg, 40Ca, 64Zn, 88Sr, 114Cd, 138Ba, 174Yb and 202Hg

The vibrational matrix elements of electric dipole moments were theoretically estimated for the electronic ground state of XH+ molecular ions (X = 24Mg, 40Ca, 64Zn, 88Sr, 114Cd, 138Ba, 174Yb and 202Hg) using the complete active space second-order perturbation theory method. Because of the large rotational constant and zero X-nuclear spin, these molecules are advantageous to be localized to a single (v, J, F) state, where v, J, F are quantum numbers of the vibrational, rotational and hyperfine states, respectively. The information of the dipole moments is very useful to discuss the period to localize the molecular ion to the (v, J, F) = (0, 0, 1/2) state and also the period to remain in this state, which is limited by the interaction with the black body radiation. The agreement of experimental and our theoretical spectroscopic constants ensures the accuracy of our results. Vibrational permanent and transition dipole moments were obtained with special care of accuracy in numerical integration. Spontaneous emission rates were calculated from the vibrational dipole moments and transition energies.

Collision Cooling of Ions Stored in Quadrupole Radio-Frequency Trap

We present a novel model for collisional energy transfer between ions and neutral molecules in the quadrupole radio-frequency trap. Calculated results quantitatively reproduce the dependence of the ion temperature Ti on the buffer gas pressure Pn, observed on Mg+ ions and several collision partners (H2, He, and CH4). It is deduced from the present model that Ti is proportional to Pn-1/3 in the low-pressure range below 10-6 Torr, in good agreement with the experimental results.

Estimated accuracies of pure XH+ (X: even isotopes of group II atoms) vibrational transition frequencies: towards the test of the variance in mp/me

This paper gives a proposal for the precise measurement of the |X1?, nv = 0, J = 0, F = 1/2, M = ?1/2 ? |X1?, nv = 1, J = 0, F = 1/2, M = ?1/2 transition frequencies of a XH+ molecular ion (X: 24Mg, 40Ca, 88Sr, 138Ba, 64Zn, 114Cd, 174Yb and 202Hg), trapped inside a linear rf-trap. The frequency uncertainty can be reduced down to the order of 10?16 because the energy shifts induced by the trapping electric field (Stark shift and quadrupole shift) and magnetic field (Zeeman shift) for the upper and lower states of the transition almost cancel each other. Measuring the variances in these vibrational transition frequencies in comparison with atomic transitions (for example 1S0?3P0 transitions of Al+ ion or Sr atoms) can be utilized for the variance test in the proton-to-electron mass ratio. Among XH+ molecular ions, 174YbH+ seems most advantageous for this purpose.

Proposed detection of variation in mp/me using a vibrational transition frequency of a CaH+ ion

This paper proposes the detection of the variation in the proton-to-electron mass ratio β by measuring a pure vibrational transition frequency of a cold CaH+ ion. The uncertainty of the this frequency can potentially be on the order of 10−16, because the uncertainties of the Zeeman and Stark shifts are lower than 10−16 and the electric quadrupole shift is zero. It is practicable to produce a CaH+ ion at a certain quantum state and perform sympathetic cooling by using the collisions with a laser-cooled Ca+ ion.

Dynamics of Trapped Ions in the Presence of Laser Cooling and Radio-Frequency Heating

We establish a theoretical model which quantitatively describes the dynamics of laser cooled ions confined in a radio-frequency (rf) trap. In our model the laser cooling efficiency and the rate of collisional radio-frequency (rf) heating are explicitly formulated. Considering the balance between these two effects, the ion temperature is determined at each trap parameter. This model precisely reproduces the laser-induced-fluorescence (LIF) line profile observed for 24 Mg+ ions.

Dependence of Temperature of Collision-Cooled Ions Stored in an RF Trap on Trapping Parameters

The kinetic property of ions stored in an RF-quadrupole trap is investigated theoretically and experimentally. We observed the dependence of the temperature of the ions on the trapping parameter (qz) and the number of ions in the presence of He buffer gas. The results are well explained by a model which represents the collisional energy transfer between ions and neutral molecules assuming a kinematic collision between them.

Effect of a Heavy Collision Partner on Ion Loss from a Radio Frequency Trap

We present a new model which represents the mechanism of loss of ions stored in a radio frequency quadrupole trap. We observed the storage time and the temperature of Mg+ ions as a function of the cooling gas (He) pressure in the presence of Kr gas, which is introduced as a heavy collision partner. Our model well reproduces the observation.

Sub-Doppler Spectroscopy by Use of Microwave Sidebands of CO2 Laser Lines Applied to the C-O Stretching Fundamental Band of Methanol

Microwave sidebands of CO2 laser lines were used as an infrared source in infrared microwave double resonance spectroscopy and infrared saturation spectroscopy to study the C-O stretching fundamental band of methanol. In the former application, rotational lines in the vCO = 1 state have been observed with good signal to noise ratios and physical processes involved in this method have been discussed. In the latter method, (vt, A/E, K) = (2, A, 4) sequence transitions in the C-O stretching fundamental band have been identified and term values for the (2, A, 4) levels in the vCO = 1 state have been determined.

Frequency measurement of pure rotational transitions of D2O using tunable terahertz spectrometer

Precise frequency measurement of the rotational lines of D2O in the terahertz (far-infrared) region is demonstrated as a case study of a high-precision far-infrared spectroscopy using a tunable radiation source. Frequencies of about 150 rotational lines of D2O were measured in the 0.5 – 5 THz region. Measured frequencies provide an excellent frequency standard for the terahertz region together with our measurements on H216O (v=0 and v2=1 vibrational states), H217O, and H218O. Molecular parameters of Watsons A-reduced Hamiltonian have been obtained to reproduce the observed frequencies.

Dynamic Properties of Polar Molecules Confined in Electrostatic Trap

We theoretically investigate the dynamics of linear polar molecules in static quadrupole electric fields. Numerical calculation shows that molecules rotating in a specific direction experience a restoring force, being three-dimensionally trapped in the center of the field distribution. We formulate the probability of Majorana transition and the trapping lifetime with a simple model of a rotating dipole. Potential depth of the electrostatic trap is quantum-mechanically estimated to be in the order of 100 mK.