Akira Terasaki

Frequency-domain interferometer for femtosecond time-resolved phase spectroscopy

A new femtosecond time-resolved interferometer was developed that utilizes interference fringes in the frequency domain to obtain simultaneously difference phase spectra (DPS) and difference transmission spectra with a multichannel spectrometer. For the first time to our knowledge, transient oscillations were observed in DPS and the spectral shift of a probe pulse was time resolved together with the rise in DPS, which is clear evidence for induced phase modulation in absorptive materials.

The application of incoherent light for the study of femtosecond-picosecond relaxation in condensed phase

A convenient technique for the ultrashort-relaxation-time measurement using temporally incoherent light instead of short pulses can be applied to the studies of relaxation processes. Theoretical studies on measuring various types of relaxation times by this method are summarized. We have applied this technique to the studies of the electronic dephasing in a polydiacetylene film, the vibrational dephasing in dimethylsulfoxide and the relaxation of optical Kerr effect in CS2 and nitrobenzene.

Spin‐polarized electronic structure of cobalt cluster anions studied by photoelectron spectroscopy

The photoelectron spectra of Co−n (3≤n≤70) were measured at the photon energy of 4.025 eV by use of a XeCl excimer laser. For Co−n with n=3, 4, and 6, the geometric and electronic structures were obtained from the spectra in comparison with the calculated spectra by the spin‐polarized DV‐Xα method. The spectra observed are reproduced reasonably well by the calculation with postulating the most probable geometrical structures. It is revealed that the 3d band with the majority spin is separated by 1.0–2.8 eV from that with the minority spin; the former is completely filled while the latter is partly filled and extends above Fermi level. The magnetic moments and the average exchange energies of these cluster anions were estimated. For Co−n with n≥7, the observed electron affinity depends linearly on the reciprocal of the cluster radius and approach the work function of a cobalt metal, as n increases. Below n=6, the electron affinity deviates from the linear dependence. This finding indicates that a size‐depe...

Femtosecond phase spectroscopy by use of frequency-domain interference

We present the principles, experimental procedures, applications, and theoretical analyses of femtosecond phase spectroscopy, which is complementary to femtosecond absorption spectroscopy. In femtosecond phase spectroscopy difference spectra of both phase and transmission are simultaneously measured with a frequency-domain interferometer, which is only slightly modified from the conventional pump–probe method. Femtosecond time-resolved dispersion relations for CdSxSe1−x-doped glass and CS2 are obtained with transform-limited pulses of 60-fs duration and 620-nm center wavelength. The results are theoretically analyzed and are well reproduced by numerical simulations. Although time-resolved data are not expected to satisfy the Kramers–Kronig (K–K) relations, the degree of discrepancy from the K–K relations is more substantial for CS2 than for CdSxSe1−x-doped glass. These results arise from the difference in the linear susceptibility and in the excited-population dynamics. The conditions for which the K–K relations are applicable to time-resolved spectra are obtained theoretically and verified experimentally. It is shown that induced amplitude and phase modulations of the probe pulses cause a deviation from the K–K relations.

Spin and orbital magnetic moments of size-selected iron, cobalt, and nickel clusters

Spin and orbital magnetic moments of cationic iron, cobalt, and nickel clusters have been determined from x-ray magnetic circular dichroism spectroscopy. In the size regime of

Energy redistribution in cluster–surface collision: I2− (CO2)n onto silicon surface

n = 10 - 15

Splitting a chemical bond with a molecular wedge via cluster-surface collisions

atoms, these clusters show strong ferromagnetism with maximized spin magnetic moments of 1~

Optical‐heterodyne‐detected induced phase modulation for the study of femtosecond molecular dynamics

\mu_B

Coordination-driven magnetic-to-nonmagnetic transition in manganese-doped silicon clusters

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Induced phase modulation of chirped continuum pulses studied with a femtosecond frequency-domain interferometer.

3d