Ultrafast conversions between hydrogen bonded structures in liquid water observed by femtosecond x-ray spectroscopy

Abstract

We present the first femtosecond soft x-ray spectroscopy in liquids, enabling the observation of changes in hydrogen bond structures in water via core-hole excitation. The oxygen K-edge of vibrationally excited water is probed with femtosecond soft x-ray pulses, exploiting the relation between different water structures and distinct x-ray spectral features. After excitation of the intramolecular OH stretching vibration, characteristic x-ray absorption changes monitor the conversion of strongly hydrogen-bonded water structures to more disordered structures with weaker hydrogen-bonding described by a single sub-picosecond time-constant. The latter describes the thermalization time of vibrational excitations and defines the characteristic maximum rate with which non-equilibrium populations of more strongly hydrogen-bonded water structures convert to less-bonded ones. On short time-scales, the relaxation of vibrational excitations leads to a transient high-pressure state and a transient absorption spectrum different from that of statically heated water.

The mechanism of ultrafast structural switching in superionic copper (I) sulphide nanocrystals

“…A calculation of the temperature of the nanocrystals after carrier thermalization, but before the onset of any phase transformation, provides the thermal-driving force for the phase transformation. Within the extinction depth of the light, the temperature increase caused in a material by an incident laser pulse may be described by the equation DT ¼ aF CN ¼ 572 C, where a (1.92 Â 10 5 cm À 1 ) is the optical cross-section, F is incident laser fluence (8 mJ cm À 2 ), C is the specific heat (76.3 J/mol K) and N is the molar density 44,10 . Note that one does not include the latent heat of the superionic transformation when calculating the driving force temperature, as the low-temperature phase has only been superheated and has not yet transformed.…”

“…These are subsequently dispersed spatially from the background picosecond X-rays, and slits are used to select the femtosecond X-rays, with a contrast ratio better than 2:1 at the Cu L 3 edge 43,44 . X-ray detection is the same as already described.…”

Charge transfer to solvent dynamics in iodide aqueous solution studied at ionization threshold

“…Previous long-term laser pump -XAS probe experiments on oxygen K-edge of liquid water upon infrared laser pump [119,120,121] and transient X-ray absorption studies on the L-edge of the transition metal complex [Fe(tren(py) 3 …”

A setup for resonant inelastic soft x-ray scattering on liquids at free electron laser light sources

“…7,8 In particular, when it comes to following molecular dynamics in solution with time-resolved x-ray spectroscopic techniques, the photon-in and photon-out based method of time-resolved RIXS (tr-RIXS) in the soft x-ray range uniquely complements femtosecond time-resolved soft x-ray absorption spectroscopy (tr-XAS). [9][10][11][12][13][14][15] The potential of femtosecond tr-RIXS has been recently demonstrated by the experimental determination of the high density and low density liquid phases of silicon 16 , which stands for the transient phases of tetragonally bound solids, including the phase diagram of ice and water.…”