Filtyp
Describing the nature and structure of molecular excited states is important in order to understand their chemical reactivity and role as intermediates in photochemical reactions. The recent implementation of X-ray absorption spectroscopy in the ultrafast time domain allows studying the electronic and structural dynamics of photochemically active molecules in solutions. In this work we present the
The introduction of pump-probe techniques to the field of X-ray absorption spectroscopy (XAS) has allowed the monitoring of both structural and electronic dynamics of disordered systems in the condensed phase with unprecedented accuracy, both in time and in space. We present results on the electronically excited high-spin state structure of an Fe(II) molecular species, [Fe II(bpy)3]2+, in aqueous
Metallica: A large contraction of the Pt-Pt bond in the triplet excited state of the photoreactive [Pt2(P2O5H 2)4]4- ion is determined by time-resolved X-ray absorption spectroscopy (see picture). The strengthening of the Pt-Pt interaction is accompanied by a weakening of the ligand coordination bonds, resulting in an elongation of the platinum-ligand bond that is determined for the first time.
We present a novel analysis of time-resolved extended x-ray absorption fine structure (EXAFS) spectra based on the fitting of the experimental transients obtained from optical pump/x-ray probe experiments. We apply it to the analysis of picosecond EXAFS data on aqueous [FeII (bpy)3] 2+, which undergoes a light induced conversion from its low-spin (LS) ground state to the short-lived (τ≈650 ps) exc
X-ray absorption spectroscopy is a powerful probe of molecular structure, but it has previously been too slow to track the earliest dynamics after photoexcitation. We investigated the ultrafast formation of the lowest quintet state of aqueous iron(II) tris(bipyridine) upon excitation of the singlet metal-to-ligand-charge-transfer ( 1 MLCT) state by femtosecond optical pump/x-ray probe techniques
We present the first structural determination of the Pt2(P 2O5H2)44- anion in solution by analyzing the extended X-ray absorption fine structure (EXAFS) spectrum of the Pt LIII edge. The data could be fit with a simple model involving single and multiple scattering paths to near and far P-atoms, bridging O-atoms, and the other Pt-atom in the binuclear complex. A Pt-Pt distance of 2.876(28) Å and a
Time-resolved x-ray absorption fine structure (XAFS) spectroscopy with pico-second temporal resolution is a new method to observe electronic and geometric structures of short-lived reaction intermediates. It combines an intense femto-second laser source synchronized to the x-ray pulses delivered into the microXAS beamline of the Swiss Light Source (SLS). We present key experiments on charge transf
The ultrafast relaxation of aqueous iron(II)-tris(bipyridine) upon excitation into the singlet metal-to-ligand charge-transfer band ( 1MLCT) has been characterized by femtosecond fluorescence up-conversion and transient absorption (TA) studies. The fluorescence experiment shows a very short-lived broad 1MLCT emission band at ∼600 nm, which decays in ≤20 fs, and a weak emission at ∼660 nm, which we
The photoinduced energy and structural relaxation of aqueous iron(II)-tris-bipyridine ([FeII(bpy)3]2+), upon excitation into its singlet metal-to-ligand charge transfer (1MLCT) band, and the population of its short-lived (≤0.6 ns) high-spin excited state have been characterized by combined ultrafast optical and X-ray spectroscopies. Polychromatic femtosecond fluorescence up-conversion reveals a ve
We describe an advanced setup for time-resolved x-ray absorption fine structure (XAFS) Spectroscopy with picosecond temporal resolution. It combines an intense femtosecond laser source synchronized to the x-ray pulses delivered into the microXAS beamline of the Swiss Light Source (SLS). The setup is applied to measure the short-lived high-spin geometric structure of photoexcited aqueous Fe(bpy) 3
We report on the observation of the solvation shell rearrangement after abstraction of the electron from aqueous I - in a laser pump/X-ray probe experiment by recording the X-ray absorption L 1 - and L 3 -edge spectra, 50 ps after laser excitation. The L 1 -edge spectra clearly identify the I 0 neutral species after excitation and suggest a substantial amount of back-transfer of charge from the s
Structural changes of the iron(II)-tris-bipyridine ([FeII(bpy)3]2+) complex induced by ultrashort pulse excitation and population of its short-lived (0.6ns) quintet high spin state have been detected by picosecond x-ray absorption spectroscopy. The structural relaxation from the high spin to the low spin state was followed over the entire lifetime of the excited state. A combined analysis of the x
The time-dependent electronic structure of Eu:SrGa 2 S 4 after excitation by a femtosecond laser pulse is investigated by time-resolved x-ray absorption spectroscopy. We observe a transient shift in the Eu L 3 edge consistent with Eu ionization.
With ultraviolet illumination, we have found a broad UV-induced absorption in the blue and some involvement of Pr ions in Pr:LiNbO 3 . Transient and stable absorption induced by UV illumination was analyzed at 457, 514, and 633 nm and could be explained by hole trap centers and iron ions. We also studied the effects of UV illumination and boundary conditions during holographic recording in the vi
We have observed ultraviolet-induced visible absorption and performed two-color holographic recording at green, red, and near-infrared light in thulium doped near-stoichiometric LiNbO 3 crystal. The diffraction efficiency and sensitivity of the recording process at all wavelengths are increased by ultraviolet gating light. Characteristics of recording in the visible are explained by a two-center
Mn-doped AlN films were prepared by magnetron reactive sputtering system. The preparation conditions were optimized to give pure single-phase AlMnN films. The films were deposited on quartz substrates. The single-phase films were obtained in argon-nitrogen pressure of 6 mTorr and a substrate temperature of 300 °C. The films typically had a thickness of 0.4 μm. The XRD pattern indicated a pure AlM
Optical spectroscopy of Tm3+-doped 59H3BO 3-20ZnO-20LiF-1Tm2O3 glass is presented. From the measured absorption spectra, radiative parameters were determined using the Judd-Ofelt (JO) theory. Excitation in the range of 750-800 nm resulted in a frequency up-converted emission at 453 nm (1D2 → 3F4). Excitation spectra and intensity dependence of the up-converted fluorescence have been investigated a
A large magneto-caloric effect is reported in a La0.8Ca 0.2MnO3 single crystal. The magnetic entropy change (ΔSM) reaches ∼7.25 J/kg K for an applied field of 5 T, which is very practical for magnetic refrigeration applications. Satisfactory agreement between the theoretical calculations on ΔSM derived in the molecular field approximation and the experimental dependency has been found.
We report ultraviolet-induced transient and stable absorption and two-color holographic recording at 514, 633, and 830 nm in thulium doped stoichiometric LiNbO 3 crystal. The gating light at 355 nm increased the diffraction efficiency and sensitivity. We found the optimum gating-recording intensity ratio for maximum diffraction efficiency and weak nonvolatile holographic storage with gating.
We investigated the photoluminescence properties of near-stoichiometric LiNbO3 crystals doped with Tb only and double doped with Tb and Fe. Excitation spectra for the emission from the 5D4 state in both crystals have been studied in the range 200-500 nm. We observed two broad ultraviolet absorption bands and discussed their relations to Tb ions. Temperature dependence of the 5D4 emission intensity
