Doppler effect in resonant photoemission from SF6: correlation between Doppler profile and Auger emission anisotropy

Fragmentation of the SF6 molecule upon F 1s excitation has been studied by resonant photoemission. The F atomiclike Auger line exhibits the characteristic Doppler profile that depends on the direction of the photoelectron momentum relative to the polarization vector of the radiation as well as on the photon energy. The measured Doppler profiles are analyzed by the model simulation that takes account of the anisotropy of the Auger emission in the molecular frame. The Auger anisotropy extracted from the data decreases with an increase in the F-SF5 internuclear distance.     

Supercontinuum generation using Raman fiber laser

Using a phosphosilicate-doped continuous-wave Raman fiber laser, a 350-m single-mode fiber, and a 50% feedback fiber Bragg grating at 1483.4 nm, we obtained a high-efficiency ultra-broadband (1434–1527 nm) supercontinuum (SC) centered at 1483.4 nm with an average output power of 2.1 W, a spectral intensity of 22.3 mWnm^-1, and a nonlinear conversion efficiency of 94%. Increasing the fiber length in the Raman cavity to 1840 m gave simultaneous SC centered at 1483.4 nm and 1239 nm. An average power of 2.3 W in the bandwidth of 1434–1544 nm and 0.2 W in the bandwidth of 1224–1257 nm is obtained. The temperature dependence of the SC was also investigated.PACS 42.55.Wd; 42.81.-i; 42.65.-k; 42.65.ReThis revised version was published in August 2003 with corrections to the affiliation of Mr. Taniguchi.     

Transient temperature profile in the gain medium of CW- and end-pumped passively Q-switched microchip laser

The transient temperature profile in CW- and end-pumped passively Q-switched (PQS) microchip laser is investigated qualitatively by treating the population inversion (thereby the thermal load) as the sawtooth function of the time. The numerical results reveal not only the dynamics of thermal buildup, but also the dependence of the quasi-steady-state temperature rise and the repetitively oscillatory amplitude on the incident pump power and the pulse repetition rate of PQS laser. The abruptly ascending branch of the repetitive temperature oscillation is synchronized with the pulsing stage of PQS laser. As the result, the abrupt temperature transition during the pulsing stage would introduce the fluctuation into the PQS pulse parameters (pulse energy, pulse width, and peak power) via temperature-dependent stimulated emission and thermal lensing effect.     

Interaction of cesium with charged oxide under UV irradiation imaged by photoemission electron microscopy

We report the first observation of electron transfer from charged SiO₂/Si(1 0 0) by ion-implantation via internal photoemission from Si by photoemission electron microscopy (PEEM) for the purpose of the microscopic control of promotion of catalyst by electron transfer from oxide support. The contrast of the PEEM image varies with the amount and kind of the implanted ion and the deposition of Cs through the formation of electrical double layer consisting of Cs⁺ and trapped electrons at trapping centers created by the implantation. It is then firmly established that oxide charging can be microscopically tuned by ion-implantation.     

Upconversion luminescence in Er-doped germanate-oxyfluoride and tellurium-germanate-oxyfluoride transparent glass-ceramics

Upconversion luminescence has been studied for Er³⁺ in a germanate-oxyfluoride and a tellurium-germanate-oxyfluoride transparent glass-ceramic using 800 nm excitation. Significantly increased upconversion luminescence was observed from transparent glass-ceramics compared with that from their corresponding as-prepared glasses. In addition to a strong green emission centered at 545 nm from ⁴S_3/2 state and a weaker red emission centered at 662 nm from ⁴F_9/2 state generally seen from Er³⁺-doped glasses, a violet emission centered at 410 nm from ²H_9/2 state and a near-ultra-violet emission centered at 379 nm from ⁴G_11/2 state were also observed from transparent glass-ceramics. The upconversion luminescence of Er³⁺ ions in transparent glass-ceramics revealed sharp Stark-splitting peaks generally seen in a crystal host. The increased upconversion efficiency is attributed to the decreased effective phonon energy and the increased energy transfer between excited ions when Er³⁺ ions were incorporated into the precipitated β-PbF₂ nanocrystals.     

Reductive displacement of the nitro group into hydrogen in primary α-nitroketones

The nitrogroup in primary α-nitroketones is converted into hydrogen with aluminum chloride and ethanethiol.     

Mechanical properties and photomechanical effect in GaP single crystals

Mechanical properdes of GaP single crystals have been investigated from 100° to 300°C by observing dislocation rosette patterns on indented specimen surfaces. It has been found that GaP has mechanical properties which are common to those of other III–V compounds or elemental semiconductors in several points: the {111} surface polarity dependence of microhardness, the mobility difference between α- and β-dislocations, and the conduction type dependence of dislocation mobility. The growth of dislocation rosettes is suppressed by baking specimens in air. Contrary to the case of II–VI compounds, illumination of visible light during indentation enhances the mobility of dislocations. These experimental results are discussed in terms of an effect of electronic charge of dislocation on its mobility.