An electrohydraulic discharge (EHD) process for the treatment of hazardous chemical wastes in water has been developed. The liquid waste in a 4-L EHD reactor is directly exposed to high-energy pulsed electrical discharges between two submerged electrodes. The high-temperature (>14 000 K) plasma channel created by an EHD emits ultraviolet radiation and produces an intense shockwave as it expands against the surrounding water. The oxidative degradation of 4-chlorophenol (4-CP), 3,4-dichloroaniline (3,4-DCA), and 2,4,6-trinitrotoluene (TNT) in an EHD reactor was explored. The initial rates of degradation for the three substrates are described by dC/dN = −k 1 C i − k 0, where dC/dN is the change in concentration per discharge; C i is the initial substrate concentration; k 0 is the zero-order term that accounts for direct photolysis; and k 1 is the first-order term that accounts for oxidation in the plasma channel region. For 4-CP in the 4-L reactor, the values of these two rate constants are k 0 = 0.73 ± 0.08 μM discharge-1 and k 1 = (9.4 ± 1.4) × 10-4 discharge-1. For a 200 μM 4-CP solution, this corresponds to an overall intrinsic zero-order rate constant of 0.022 M s-1 and a G value of 4.45 × 10-3. Ozone increases the rate and extent of degradation of the substrates in the EHD reactor. Combined EHD/ozone treatment of a 160 μM TNT solution resulted in the complete degradation of TNT and a 34% reduction of the total organic carbon (TOC). The intrinsic initial rate constant of TNT degradation was 0.024 M s-1. The results of these experiments demonstrate the potential application of the EHD process for the treatment of hazardous wastes.

In this contribution, studies of the dynamics of proton-transfer reactions in solvent cages are presented, building on earlier work [Breen, J. J.; et al. J. Chem. Phys. 1990, 92, 805. Kim, S . K.; et al. Chem. Phys. Lett. 1994, 228, 3691. The acid-base system studied in a molecular beam is 1-naphthol as a solute and ammonia, piperidine, or water as the solvent, with the number of solvent molecules (n) varying. The rates and threshold for proton transfer have been found to be critically dependent on the number and type of solvent molecules: n = 2 for piperidine and n = 3 for ammonia; no proton transfer was observed for water up to n = 21. With subpicosecond time resolution, we observe a biexponential transient for the n = 3 cluster with ammonia.From these observations and the high accuracy of the fits, we provide the rate of the proton transfer at short times and the solvent reorganization at longer times. From studies of the effect of the total energy, the isotope substitution, and the number and type of solvent molecules, we discuss the nature of the transfer and the interplay between the local structure of the base solvent and the dynamics. The effective shape of the potential energy surface is discussed by considering the anharmonicity of the reactant states and the Coulombic interaction of ion-pair product states. Tunneling is related to the nature of the potential and to measurements specific to the isotope effect and energy dependence. Finally, we discuss a simple model for the reaction in finite-sized clusters, which takes into account the proton affinity and the dielectric shielding of the solvent introduced by the local structure.

Vibrational predissociation of I, X, (X = Ne, Ar) van der Waals clusters are studied in realtime using picosecond pump-probe (LIF) and molecular beam techniques. The state-to-state rates of vibrational predissociation are measured for specific vibrational levels v] by monitoring the rise of nascent I,. Here, we report our study of k(uj.uj) 1,X(&u;) + I, (B,vj) + x.For I, Ne, the values of r = k -' (v],z$) decrease nonlinearly from 2 16 ps for v] = 13 to 53 ps for vi = 23. For 1,Ar (B,vj), which undergo electronic and vibrational predissociation, the risetime of the nascent I, is found to be 70 ps when 0; = 18 and 77 ps when v] = 21. A number of theoretical models for vibrational predissociation (the energy-gap law, the momentum-gap law, quantum and classical calculations) are compared with our experimental results in an attempt to understand the key features of the dynamics and the potential energy surface.

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In this paper (III) we report real-time studies of the picosecond dynamics of iodine in Ne clusters IzNe,( Iz = 2-4) + IT + nNe. The results are discussed in relation to vibrational predissociation (VP), basic to the 1,X systems, and to the onset of intramolecular vibrational-energy redistribution (IVR). The latter process, which is a precursor for the evaporation of the host atoms or for further fragmentation, is found to be increasingly effective as the cluster size increases; low-energy van der Waals modes act as the accepting (bath) modes. The reaction dynamics for I,Ne, are examined and quantitatively compared to a simple model which describes the dynamics as consecutive bond breaking. On this basis, it is concluded that the onset of energy redistribution is observed in 12Ne2. Comparison of 1,Ne and I,Ne2 to larger clusters (n=3,4) is accomplished by introducing an overall effective reaction rate. From measurements of the rates and their dependence on uf, the initial quantum number of the I3 stretch, we are able to examine the dynamics of direct fragmentation and evaporation, and compare with theory. I. INTRODUCTIONThe reaction dynamics of size-selected van der Waals (vdW) clusters form a basis for understanding the interplay between intramolecular vibrational-energy redistribution (IVR) and the direct fragmentation by vibrational predissociation (VP). For the case at hand, halogen-rare gas clusters, there are two interesting regimes for the dynamics which are determined by the effective size of the cluster. For small clusters, the "small-molecule" description of the dynamics may apply as in the case of I,He, I,Ne, and 1,Ar (n= 1 ), discussed in Papers (I) ' and (II).2 In this case, the dynamics of VP are governed only by the coupling between the initially prepared metastable bound state and the final dissociation continuum (see Fig. 1).For the larger clusters, the density of states plays an important role in the dynamics, perhaps reaching the statistical limit of the "large-molecule" case. The initially prepared state in this case couples not only to the mode(s) of the reactive coordinate(s), but also to nonreactive "bath modes" whose number increases with n. The transition from one regime to the other is interesting to explore, both theoretically and experimentally.An important question concerning the larger clusters (n > 1) relates to the mechanism: Do the rare gas atoms directly break one at a time (a sequential mechanism), or do they indirectly fragment following energy redistribution? And if indirect fragmentation is the pathway, does it occur by VP or evaporation? Consider, for example, 12Ne2. I,*Ne(vf--l)+It(uf-2)+Ne,where ui is the vibrational quantum number of the initial iodine stretch. These direct pathways in Eqs. ( 1) and (2) contrast a path in which energy is dissipated to the modes of the surrounding atoms/I, cluster. Because of the presence of the two neons, energy redistribution from the I2 stretch to nonreactive modes could compete with direct VP, leading to a new channel I~Ne2(uf)~I~Ne~(...