The transient volume change of $\ensuremath{\alpha}$-quartz and fused silica induced by irradiation with an electron pulse has been measured above 80 K. It is shown that changes optical absorption due to the ${{E}_{1}}^{\ensuremath{'}}$ centers (oxygen vacancies) decay in parallel per center order a unit molecular volume. results show unambiguously recombination-induced defect formation occurs Si${\mathrm{O}}_{2}$ but defects created are not stable even at low temperatures.

Optical-absorption and emission spectra are presented for ${\mathrm{Ho}}^{3+}$ ions in fluorozirconate (ZBLA) glass [the nominal composition of ZBLA (in mol%) is 57, ${\mathrm{ZrF}}_{4}$; 34, ${\mathrm{BaF}}_{2}$; 5, ${\mathrm{LaF}}_{3}$; 4, ${\mathrm{AlF}}_{3}$]. The measured oscillator strengths radiative rates several transitions were compared with calculated values. Nonradiative transition the excited states determined by difference between rates. Multiphonon energy-transfer effects...

Linear polarisation, with respect to the z axis, and effect of subsequent laser-induced excitation on luminescence transient optical absorption induced by irradiation crystalline SiO2 an electron pulse have been studied. It is found that spectrum consists two bands peaked at 2.8 eV 2.5 transition dipole moment former, which has shown be intrinsic, nearly parallel while latter x axis. In addition 5.2 band, a satellite band 4.2 pulse. For both these bands, dipoles are not any axes. Subsequent...

A scanning tunneling microscopy study and ab initio total energy calculations have identified the atomic-level structure of novel sp;{3}-bonded carbon nanoscale domains formed dynamically from graphite by femtosecond-laser excitation. The is characterized a pseudo sp;{3}-bonding configuration that results in inward displacement surface atoms 0.5 every third row along [11[over ]00] orientation. This structural periodicity unique differs conventional phases diamond.

We have developed a compact ultrafast electron diffractometer, consisting of laser-driven rf photocathode that generates 3.0 MeV probe pulses, three-stage lens optics, and custom-built detector for relativistic electrons. High-quality single-shot transmission diffraction has been detected from 180-nm-thick Si single crystals, with an excellent special resolution diffracted beams; the spot width 0.02 A−1 is obtained. The pulse estimated to be 100 fs in duration. Characteristics beam other...

The dynamics of momentum-dark exciton formation in transition metal dichalcogenides is difficult to measure experimentally, as many momentum-indirect states are not accessible optical interband spectroscopy. Here, we combine a tunable pump, high-harmonic probe laser source with 3D momentum imaging technique map photoemitted electrons from monolayer WS2. This provides momentum-, energy- and time-resolved access excited on an ultrafast time scale. high temporal resolution the setup allows us...

The excitation spectrum of the 2.8-eV luminescence band crystalline Si${\mathrm{O}}_{2}$ has been measured in a photon energy range between 6 and 14 eV at 77 K. We find that onset occurs 8.3 eV, which is nearly equal to fundamental optical absorption edge Si${\mathrm{O}}_{2}$. This result supports strongly model due radiative recombination self-trapped excitons.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTFluorescent copper(I) complexes: structural and spectroscopic characterization of bis(p-toluidine)bis(acetonitrile)tetraiodotetracopper bis[(p-chloroaniline)(acetonitrile)diiododicopper] tetrameric complexes mixed-ligand characterNigam P. Rath, Elizabeth M. Holt, Katsumi TanimuraCite this: Inorg. Chem. 1985, 24, 23, 3934–3938Publication Date (Print):November 1, 1985Publication History Published online1 May 2002Published inissue 1 November...

Copper(I) iodide forms complexes of stoicheiometry 1:1:2 and 1:1:1 with quinoline(quin). [{Cul(quin)2}2](1)[monoclinic, space group A2/a, a= 25.620(6), b= 7.495(2), c= 20.314(4)Å, β= 111.60(1)°, Z= 8, R= 0.082 for 1 828 observed reflections] crystallizes isolated rhombohedra Cu2I2, each copper bound to the nitrogen atoms two quinoline groups. Complex (1) displays a broad-band emission spectrum (λmax. 620 nm) which is independent temperature. [Cu4I4(quin)4](2)[triclinic, P, 12.161(8),...

Abstract Current development of the research radiation damage in ionic solids is reviewed. Emphasis placed on correlation between elementary processes and atomic electronic structures materials. Both induced by excitation elastic collision are treated. For former two crucial processes, self-trapping excitons formation stable Frenkel pairs from self-trapped several materials, discussed terms Deficiency available data knock-on threshold energies pointed out. Available information produced...

We performed relativistic ultrafast electron diffraction (UED) measurements of the structural dynamics photoexcited gold nanofilms and developed an atomistic model, based on two-temperature molecular (2T-MD) method, which allows us to make a direct comparison time evolutions measured calculated Bragg peaks. The quantitative agreement between temporal experimental theoretical peaks at all fluences suggests that 2T-MD method provides faithful representation evolution films. results reveal...

The rapid development of the computational methods based on density functional theory, one hand, and time-, energy-, momentum-resolved spectroscopy, other allows today an unprecedently detailed insight into processes governing hot-electron relaxation dynamics, and, in particular, role electron–phonon coupling. Instead focusing a particular method, theoretical or experimental, this review aims to treat progress understanding coupling which can be gained from both, basis recently obtained results.

Despite the fact that phase-change materials are widely used for data storage, no consensus exists on unique mechanism of their ultrafast phase change and its accompanied large rapid optical change. By using pump-probe observation method combining a femtosecond laser an x-ray free-electron laser, we substantiate experimentally that, in both GeTe Ge_{2}Sb_{2}Te_{5} crystals, rattling motion mainly Ge atoms takes place with keeping off-center position just after femtosecond-optical-laser...

The ab initio calculations of phonon dispersions and nonthermal forces along structural deformation paths were used to study solid-to-solid phase transitions in photoexcited tungsten. We assumed that electronic excitation can be described by an temperature demonstrated nonthermal, i.e., caused purely excitation, bcc-to-fcc bcc-to-hcp occur for temperatures between 1.7 4.3 eV. These result from soft modes the $\ensuremath{\Sigma}$ line Brillouin zone. Structural path at different indicate...

The rearrangement of a material's electron density during laser irradiation leads to modified nonthermal forces on the atoms that may lead coherent atomic motions and structural phase transformation very short time scales. We present ab initio molecular dynamics simulations martensitic solid-solid in tungsten under conditions strong electronic excitation. is ultrafast, taking just over picosecond, follows tetragonal Bain path. To examine whether bcc-fcc could occur irradiation, we use...

The controversial relationship between the intrinsic 1.9 eV photoluminescence (the R band), 2.0 and 4.8 excitation/optical absorption bands is examined for 11 specimens with different OH, Cl, O2 concentrations irradiation histories. direct relation found intensities of R-band luminescence measured 4.0 (IUV) or resonance (1.94 eV) excitation (Ires), although it slightly superlinear, Ires∝(IUV). deviation from exactly constant ratio band in glass samples attributed mainly to inhomogeneous...

Optical-absorption change following photoexcitation of the lowest triplet self-trapped exciton (STE) in NaCl has been measured femtosecond time regime. It is found that a short-lived intermediate state generated within 1 ps and decays accompanied by restoration STE. An oscillation population STE with period 1.1 was observed. Formation Frenkel pairs to occur not at initial stage relaxation but as result leading

The transient optical absorption and luminescence induced by irradiation of amorphous SiO2 with an electron pulse have been measured. It is found that the spectra do not depend on impurities a strong peak at 5.3 eV satellite 4.2 eV. energy band to show blue shift as time after increases. By means cascade excitation experiment, eV, shown arise from same centre, which ascribed self-trapped exciton or metastable excited state accompanied large lattice distortion.

The dynamical relaxations of photogenerated hot carriers in the X valley Si have been studied using time-resolved two-photon photoemission spectroscopy. Intravalley scattering is completed within 100 fs to form a quasiequilibrated electron distribution near conduction-band minimum, while maintaining about half excess energy given electrons. relaxation follows with 240-fs time constant that independent energy.

We study ultrafast scattering dynamics of hot electrons photoinjected with high excess energies in the \ensuremath{\Gamma} valley conduction band GaAs, using time- and angle-resolved photoemission spectroscopy ab initio calculations. At rates order 10 fs, packets are transformed into hot-electron ensembles (HEEs) quasiequilibrated momentum space but not energy space. The relaxation HEEs takes place as a whole on longer time scale dependent only energy, irrespective momenta electrons. Both...

The intrinsic 1.9-eV photoluminescence band (the R band) in neutron-irradiated synthetic silica glass has been studied using site-selective excitation the 2.0 eV absorption and transient spectral hole-burning techniques. measurements of low-energy wing zero-phonon line intensity distribution function confirm predicted nearly Gaussian shape with a peak at 1.93 half-width 86 meV. homogeneous emission contour (``single-site spectrum'') evaluated by selective saturation method, revealing, phonon...

Laser-induced structural changes on the Si(111)- $(7\ifmmode\times\else\texttimes\fi{}7)$ surface were studied for laser fluences below thresholds of melting and ablation. The adatoms reconstructed structure are removed selectively by an electronic process, Si atoms in ground state ejected with a peak translational energy 0.15 eV. process this bond breaking exhibits site-sensitive efficiency which shows resonant wavelength dependence is highly superlinear respect to excitation intensity.

Two-photon photoemission (2PPE) spectroscopy is used to reveal dynamic relaxation of highly excited electrons generated by 3 eV photons in Si. Monochromatic 2PPE at probe-photon energies ranging from 3.2 3.5 reveals a coherent peak the valence band maximum, and transiently populated near L${}_{1}$ conduction band. Time-resolved measurements show that injected into L valley undergo L-to-X intervalley scattering with time constant 180 fs 293 K. A deformation potential 1.2...

The time evolution of the Bragg peaks photo-excited gold nanofilms is measured using transmission ultrafast electron diffraction (UED) with 3.0 MeV pulses and corresponding structure calculated two-temperature molecular dynamics (2T-MD). good agreement obtained between peaks, over full experimental timescale, enables lattice temperature effects structural changes to be disentangled for first time. demonstrates that 2T-MD a reliable method solving inverse problem determination laser...