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The theories of R. Marcus and of Levich for electron transfer reactions are criticised. Electron exchange current is calculated on the basis of a time dependent perturbation theory, by using a simple model. Distortions introduced in the theory by oversimplification of the model are discussed. In the resulting equation for the exchange current, the exponential term is identical to the one of the two mentioned authors. The preexponential term is different. A class of electrode reactions is discussed for which the kinetics are completely different. In all cases, no distinction may be done between adiabatic and non-adiabatic reactions.

Phenomena induced in ethylene subsequent to low intensity c. w. irradiation with several lines of the CO2-laser emission are investigated by means of a time-of-flight technique and mass spectroscopic analysis on-line. Variety of behaviours of the different lines is confirmed: some excite preferentially 1ν7, others excite probably a higher vibrational level (2ν7). Vibrationally hot ethylene is converted into a new substance, which may be an excimer stabilized excited state. This substance is shown to react with oxygen.

Electrocatalytic reduction of acetone to propane on a platinum catalyst in acid electrolyte is studied. By applying square wave modulation to the electrode potential, it is possible to determine the kinetics of the formation of adsorbed intermediates. Voltage and H+ -ion concentration effects on the observed relaxation times give arguments for a discussion of the detailed mechanism of the process.

By using a square wave modulation technique, a fast reversible step is isolated ahead of the rate determining process for the reduction of butanone to butanol-2. By comparison with analogous results obtained previously for the reduction of acetone to propane, it is concluded that this reversible step is situated ahead of the branching between the alcane and alcohol paths.

Butanone is reduced to butane and butanol-2 on Pt in H2SO4 electrolyte. Oscillating accumulation of intermediates in the butane reaction is observed. Their chemical nature is discussed: a chemisorbed butyl radical and interstitial hydrogen atoms.

Chemical processes in C2H4 irradiated with CO2-laser pulses are investigated. In the higher pressure domain (>5 torr) a focused laser beam initiates a plasma, while C2H4 dehydrogenises to C2H2. If the beam is not focused, there is no dehydrogenation but C2H4 is capable to react with HCl. In the very low pressure domain a new chemical reaction is observed which is interpreted as being a consequence of multiple photon absorption. Isotope selectivity is investigated.

Thermodynamic relations are derived from first principles of mechanics for non-equilibrium processes. Since the key role herein is played by the law of increase of entropy, the latter is analyzed at first. It is shown that its derivation for isolated systems does not allow one to say too much about thermodynamic properties in non-equilibrium conditions. From there on, the notion of quasi-isolated systems is introduced, for which it is possible to describe the state of macroscopic systems by a collection of intensive variables. The latter are the differentials of the entropy with respect to the given set of extensive constraints. Arguments are developed showing that the dynamics of irreversible relaxation of non-equilibrium systems consists of two qualitatively different steps. The theory is applied and verified by describing transport processes and calculating the corresponding coefficients. Structure formation and transition to turbulence are equally formalized in the thermodynamic framework., Comment: 43 pages revtex, 2 figures. Presented at the Workshop on Time-Reversal Symmetry in Dynamical systems, Warwick, U.K., 9th-20th December 1996

The laser is treated as a thermodynamic machine where production of radiation is the result of entropy creating spontaneous flows of energy and polarization through the system. One of the laws of thermodynamics governing flows of extensive properties is the symmetry principle of Curie and Prigogine. It determines how much flows are coupled. Going back to the first principles of statistical mechanics and using aforementioned symmetry requirements, a set of alternative Bloch equations is derived. The impact of the new formulation on laser physics is developed. It leads to a set of new conclusions for spontaneous pulsating regimes, for the spectral line shape of coherent radiation, for saturation effects, etc.

Multiphoton vibrational excitation of ethylene with CO2-laser light has been investigated. Two different types of results are shown according to which laser line was used for excitation. Energized ethylene converts to the triplet state. This reaction is mode selective and is favoured by certain laser lines.

Using the framework of statistical mechanics, the laser is treated as a thermodynamical machine which converts heat into electromagnetic energy. Conditions are defined for smooth emission and for spontaneous pulsing (relaxation oscillation). The treatment allows precise predictions about the phase fluctuations of the produced radiation. The results are applied to the action of laser radiaton of molecular oscillators. The role of phase fluctuations on the process of multiphoton absorption of energy is stressed.

This paper is on irreversible thermodynamics. It will be shown that the non-linear properties of coherently driven systems depend on irreversible flows of extensive properties between the driven system and its surroundings (the "thermostat"). The kinetics of the flows and especially their degree of coupling are determined from first principles on the basis of statistical arguments. There is unfortunately much confusion in the literature about the principles of thermodynamics and about its relevance in non-equilibrium systems. This question has been fully discussed in a long paper (1) and a note (2) to which the reader is kindly asked to refer for justification of the method and other details.

On the basis of a thermodynamic treatment of driven harmonic oscillators in a coherent field it is demonstrated that resonant molecules are attracted by the high-field region of a finite-width laser beam. This phenomenon has been observed experimentally. The same thermodynamic treatment explains the pressure and the fluence dependence of “Collisionless” multiphoton excitation. Saturation phenomena (Lamb dip) are shown to be caused by the distortion of the translational velocity distribution of oscillators in a nearly resonant field.

The action of 29 rotational lines of the CO2 laser on ethylene at low pressure (1 to 2 Torr) and subsequent relaxation are investigated by means of a time of flight device, coupled to a mass spectrometer. In all cases activation is sufficient to convert ethylene efficiently into its triplet state. Two different behaviors of laser excited ethylene are discussed. They depend on which line the laser is tuned to. Considering that two IR active modes extend their rotational manifolds over the range covered by CO2 laser radiations (ν7 and ν10), it is believed that the different laser lines energize selectively either one of them.

The pressure effects of CO2‐laser radiation in low pressure unbuffered ethylene are measured. The experimental results show two distinct and oppositely signed pressure excursions which the theory (irreversible thermodynamics) ascribes to osmosis or coherent diffusion (dominant at low pressure) and heating (higher pressure measurements). The two relaxation times and the intensities of the effects are measured.

The action of 29 rotational lines of the CO2 laser on ethylene at low pressure (1 to 2 Torr) and subsequent relaxation are investigated by means of a time of flight device, coupled to a mass spectrometer. In all cases activation is sufficient to convert ethylene efficiently into its triplet state. Two different behaviors of laser excited ethylene are discussed. They depend on which line the laser is tuned to. Considering that two IR active modes extend their rotational manifolds over the range covered by CO2 laser radiations (ν7 and ν10), it is believed that the different laser lines energize selectively either one of them.

Pressure transients are observed in absorbing gases at low pressure in a non-resonant spectrophone. At very low pressure (transition saturated) the transient is negative on irradiation. Interpretation is given in terms of thermodynamics of laser driven systems. The local value of the partition function of resonant molecules is shwon to be a function of the driving beam's intensity. The law of mass action predicts then accumulation of the resonant particles in the high intensity regions of the beam.

The influence of adsorbed hydrogen on the electroreduction of acetone in H2SO4 medium on platinized platinum is studied. Two independent paths are accessible for the reaction; one leads to propane and the other to isopropanol. The existence of two types of adsorption for hydrogen is confirmed; one of them is interstitial. The activity of the electrode for the reduction of acetone depends on its interstitial hydrogen content. Besides its influence on the adsorption properties of the electrode, interstitial hydrogen is not directly involved in the reaction path leading to propane, whereas this type of hydrogen has a more important role in the reaction path leading to isopropanol. The hydrogen atoms in the methyl groups of acetone undergo isotopic exchange with the electrolytic hydrogens, during adsorption on the electrode. The degree of exchange depends on the voltage and on the activity of the electrode.