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We use ultrafast x-ray absorption spectroscopy to determine the solvent structure change upon laser abstraction of the electron from I. The transition from hydrophilic to hydrophobic occurs over 4 ps during which a transient I-OH2 species is formed.
An X-ray absorption fine-structure spectroscopy (XAFS) cell that is suitable for solution-phase studies of the light elements in the series from Na+ and Ca2+ is described. This cell has an ultra-short pathlength that can be remotely adjusted using a miniature stepper-motor drive and thereby readily provides transmission pathlengths in the range from submicrometer to several hundred micrometers. Th
We show, through a combination of density function theory-based molecular dynamics simulations (DFT-MD) and experimental X-ray absorption fine structure spectroscopy (XAFS) studies, that the iodate ion (IO 3 -) contains a local region that is strongly hydrated as a cation. The local region adjoining the I atom is sufficiently electropositive that three hydrating waters are oriented with their O at
Picosecond and femtosecond X-ray absorption spectroscopy is used to probe the changes of the solvent shell structure upon electron abstraction of aqueous iodide using an ultrashort laser pulse. The transient L 1,3 edge EXAFS at 50 ps time delay points to the formation of an expanded water cavity around the iodine atom, in good agreement with classical and quantum mechanical/molecular mechanics (
Meeting adherence is an important element of compliance in treatment programmes. It is influenced by several factors one being self-efficacy. We aimed to investigate the association between self-efficacy and meeting adherence and other factors of importance for adherence among patients with alcohol and drug addiction who were undergoing an intensive lifestyle intervention. The intervention consistMeeting adherence is an important element of compliance in treatment programmes. It is influenced by several factors one being self-efficacy. We aimed to investigate the association between self-efficacy and meeting adherence and other factors of importance for adherence among patients with alcohol and drug addiction who were undergoing an intensive lifestyle intervention. The intervention consist
We present the extension of time-resolved optical pump/x-ray absorption spectroscopy (XAS) probe experiments towards data collection at MHz repetition rates. The use of a high-power picosecond laser operating at an integer fraction of the repetition rate of the storage ring allows exploitation of up to two orders of magnitude more x-ray photons than in previous schemes based on the use of kHz lase
We review our recent studies of excited state structures and dynamics of chemical and biological systems with pico- and femtosecond X-ray absorption spectroscopy in the liquid phase.
We present ultrafast x-ray emission studies of photoexcited aqueous iron tris-bipyridine with 70 ps temporal resolution to monitor the spin state changes in this spin-crossover complex.
Understanding the initial steps during ultrafast molecular reactions involving large spin state changes is a vital goal in structural dynamics research. These involve knowledge of the geometric structure of the system. Ultrafast X-ray absorption spectroscopy with 50-100 picosecond time resolution establishes the geometric structure of the short-lived (τ = 0:6 ns) high spin state. Here we focus on
(Figure Presented) Ultrafast spin probe: A short-lived transient species of light-excited [Fe(bpy) 3 ] 2+ (bpy = 2,2′-bipyridine) shows geometry variations that correspond to excitation to a high-spin state, in which the spin momentum of Fe" has now been directly determined to be S = 2 by spin-sensitive ultrafast X-ray emission spectroscopy.
The L3 X-ray absorption spectrum of aqueous iodide is reported, and its EXAFS is compared to theoretical spectra reconstructed from the radial distribution function of the iodide hydration obtained from classical, hybrid Quantum Mechanics Molecular Mechanics, (QM/MM) and full quantum (density functional theory, DFT) molecular dynamics simulations. Since EXAFS is mainly sensitive to short distances
Ultrafast X-ray absorption spectroscopy is a powerful tool to observe electronic and geometric structures of short-lived reaction intermediates. The ab initiofeff9 code is applied to simulate the Pt L3-edge XANES spectrum of the photocatalytic diplatinum molecule [Pt2(P2O5H2)4]4− and the photo-induced changes that occur therein. The spectra are interpreted within a XAFS-like scattering theoretical
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
