Pure liquids, electron relaxation

Figure 2. Transient absorption spectrum of visible aqueous electrons generated by different exdtation methods of pure liquid water pulse radiolysis (60j, pico-second pulse photolysis (58), and femtosecond UV photolysis (6). The long-lived spectra obtained by three different pulsed methods correspond to a broad absorption band of relaxed hydrated electrons (in an s-like ground state) centered around...

Figure 3. Time dependence of different electron-transfer trajectories in molecules of pure liquid water at room temperature. The femtosecond UV excitation of water molecules (2X4 eV) triggers either an ultrafast electron photodetachment with the formation of hydronium ions and a nonadiabatic relaxation of excited p-like hydrated electrons (high photochemical channel), or concerted electron-proton transfer (low photochemical channel) (56, 72). The characteristic time of each trajectory is reported on the curve.

In Section I we briefly discuss the relationship between the theoretical parameters and experimental observables in these experiments in terms of the spectroscopy of electrons in liquids. Experimental techniques are considered in more detail in Section II, while the data from electron solvation in pure liquids are reviewed in Section III in the context of the molecular dynamics of the host liquid. Section IV presents current results on electron trapping in very dilute polar systems and leads to speculation on mechanisms of electron localization. In Section V the first direct observations of a photoselective, laser-induced electron-transfer process are presented, following which we summarize as yet unresolved issues and speculate on future directions in the laser spectroscopy of electron-relaxation processes. 

Fig. 3. A Risetime of absorption at 720 and 1230 nm. The smooth lines represent the computer best fits assuming an appearance time of 110 fs for the infrared specie (1230 nm) and its relaxation toward the solvated state in 2 0 fs. B Transient absorption spectra of the electron at 200 fs and 2ps following photoionization of pure liquid water with 100 fs laser pulse (A=310 nm, eV).

Since the row nuclei in the crystallising strained melt act as reinforcing frame structure carrying most of the load in the strained liquid, the not yet crystallised melt inside the frame is able to relax almost completely. It hence either crystallises in conventional manner on the surface of the row nuclei yielding the cylindrites or forms new conventional primary nuclei yielding spherulites as shown by electron microscopy of thick nylon 6 fibres as spun. The coexistence of both structural elements in the fibre as spun with a very small fraction of material in row nuclei explains the poor mechanical properties of such a material and the similarity of fibrous structure obtained after drawing with that obtained from purely spherulitic films. 

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