Thermal diffusivity has been investigated in ordered double perovskite Sr2FeMoO6 measn of transient surface grating technique in te temperatue rage of 300-450K. The thermal diffusivity showas an apprecialve decrese form 39mm/2s at 300K to 37mm/2 at 360K in the ferromagnetic phase, and then steeply drops to 10mm2/s with furtherincreasing temperature above the critical temperature Tc～380K. Such an abrupt decrease of the thermal diffusivity has been ascribed to the structural phase transition at Tc. We further investigate the lattice effect on the thermal diffusivity in A2FeMoO6 (A=Ca, Sr and Ba) by substitution of CA2+or Ba2+ ions for Sr2+ions at 300K. We find that the thermal difusivity increases form 35mm2/s for A=Ca to 41mm2/s for A=Ba. Considering the change of the Fe-O-Mo bond angle and hence the wider one-electrom bandwidth W.

The second-harmonic sound beam nonlinearly generated by a conical source is analytically described It is shown that the radial second-hamonic beam is distributed as the Bessel function and independent of the porpagation distance. Anoher important feature is that the beamwidth of the second-harmonic component is just equal to 1/2 time that of the fundamental, not 1/√2 times in the general cases. A potential application of this beam in the acoustic noninearity parameter B/A imaging or measurement is also discussed.

The themal diffusivity has been ivestigatedin double perovskite Sr2MMoO6 (M=Fe, Mn and Co) by means of the mirage effect. We have found that the thermal diffusivity of metallic Sr2FeMoO6 is 0.39 cm2/s, wihich is larger than that (0.33cm2/s) of insulating Sr2MnMoO6 and Sr2CoMoO6. We further investigate the substitution effects of the La3+ions for the Sr2+ions in Sr2FeMoO6 and Sr2MnMoO6, and have found that the thermal diffusivities of both samples significantly increase with the La cncentration. Such an enhancement of the thermal diffusivities has been a scribed ot occupation of the extra itinerant electrons on te conducion Mo4d band.

Electronic structures of halogen bridged mixed-valence (MV) complexes Cs2Au2X6 (X=I, Br, and Cl)have been investigated by means of reflectivity measurements. We have observed five polarization-dependent opti-cal transitions in the energy range of 0.6-5.5eV. The lower-lying three bands below～3eV are due to the intermolecular transitions from AuX2 to Aux4 molecules, while the others are assigned to the intramolecular transitions. The optical ap Egap increases from 1.31 eV for X=I to 2.04 eV for X=Cl, due to enhancement of the nearest-neighboring Coulomb repulsion V and the Jahn-Teller distortion of AuX4 (S). We further investi-gated extemal pressure effects on the electronic state, and found pressure-induced disappearance of the Raman-active Au-Br stretching modes, which indicates an electronic phase transition from the MV state to a single-valence (SV) state.

Two kinds of cadmium sulfide (CdS) particulate films have been generated in situ by exposing stearic acid (SA) Langmuir monolayer at the air-aqueous CdCl2 interface to hydrogen sulficde(H2S) gas: particulate films composed of oriented rodlike nanocrystals (A-type particulate films), and those of dotlike nanocrystals which formed a stripelike domain with straight edges aligned with 6-fold symmetry(B-type particulate fims). The SA-coated CdS particulated films were transferred to a solid substrate and examined by transmission electron microscopy (TEM) and photoacoustic spectroscopy (PAS). The dark field image and the transmission particulte fims in detail. The PAS of the CdS particulate fims coposed of the oriented rodlike nanocrystals shows a new peak at 417.5nm. This peak implies some new physical phenomena corresponding to the oredred alignmert of the semiconductor nanocrystals. which exists in the ordered nanosystems. The novel synthesis method described here leads to the fabricaiton of the highly oriented semiconductor quantum wires and provides a new method to investigate the structure of the Langmuir monolayer at the air-water interface.