Georges Vigneron

Ultrafast events in the electron photodetachment from the hexacyanoferrate(II) complex in solution

Abstract Following excitation of the hexacyanoferrate(II) complex in water with a 40 fs laser pulse at 267 nm, the absorption of the hydrated electron rises with a global time constant of 510 fs, whereas the characteristic absorption of the hexacyanoferrate(III) appears almost instantaneously. A transient absorption band around 490 nm is tentatively assigned to the charge-transfer-to-solvent (CTTS) state of the hexacyanoferrate(II). Its ultra-rapid decay (≪60 fs) is due to the electronic repulsion between the electron and its parent core.

Three-photon absorption cross-section of simple molecular liquids

Abstract Three-photon absorption coefficients and the corresponding three-photon absorption cross-sections of several simple molecular liquids at 400 nm are obtained from intensity dependent transmission measurements. The peak power of the femtosecond laser pulses was varied from 10 12 to 10 15 W/m 2 . For all liquids investigated the three-photon absorption coefficient was found to be close to 1×10 −27 m 3 /W 2 .

Nanosecond kinetics of hydrated electrons upon water photolysis by high intensity femtosecond UV pulses

We report a nanosecond laser study of the transient absorption of hydrated electrons generated by multiphoton ionisation of liquid water upon excitation at 266 and 400 nm by femtosecond pulses with power densities higher than 1 TW/cm2. For both wavelengths, as the pump power density increases, the signal amplitude increases and the decay becomes faster proving that more electrons are produced. However, we show that in the nanosecond time range, under pump power densities higher than 1 TW/cm2, the distribution of the hydrated electrons is not uniform along the optical pathway of the pump beam in the water sample.

Water reduction by photoexcited silica and alumina

Excess electrons in solvent are amongst the most fascinating chemical species, at the very edge between physics and chemistry. In this contribution, we report the use of silica and alumina photochemistry to create and stabilize aqueous solutions of electron.

Experimental and theoretical study of the degradation of malonamide extractant molecules under ionizing radiation

The behavior of three malonamides diluted in octane and submitted to ionizing radiation has been studied by means of in situ infrared spectroscopy, electrospray ionization mass spectrometry and quantum chemistry calculations. The major channel at low dose for a malonamide with ethyl groups on the nitrogen atoms and no substituent on the central carbon atom arises from the addition of an octyl group from the solvent. Adding alkyl chains on the nitrogen atoms and/or an alkyl chain on the central carbon atom weakens the central C–C bond which is then preferentially cleaved upon irradiation. The other bond cleavages (both C–N and C–H cleavages) are then detected when increasing the dose.

Interaction of terawatt laser pulses with neat water

Femtosecond time-resolved experiments in neat water under terawatt ultraviolet laser pump power density are reported. For the first time, the formation of a decimolar concentration of hydrated electron is demonstrated. The contribution of non-geminate recombination is discussed.