Surface-enhanced Raman scattering (SERS) of adenosine triphosphate molecules (ATP) adsorbed on silver electrodes is studied. Voltage dependence, concentration dependence, and pH value dependence of the SER spectra are presented. All these can be understood by considering that these molecules are adsorbed on the silver electrodes through adenine rings with end-on or flat-on orientation. The effect of divalent metal on the spectra is discussed.

PHYSICAL REVIEW LETTERS 30 AUGUST 1976 ducting microbridge irradiated by microwaves, can be understood by the fact that a low-energy quasiparticle is more effective in blocking the pairing process than higher energy quasiparticles. Here, our calculation shows that a superconductor irradiated by microwave can actually have a quasiparticle density smaller than its equilibrium value. This can also lead to an increase in the energy gap and critical current.18 Please note that this excess quasiparticle density is not the same as that defined in Ref 0 7 0 19 We believe that the flat I (V) characteristic for a lowtemperature nonequilibrium tunneling junction found byThe resistivity of an aggregated film of conducting material has been well known to exhibit an abrupt fall over several orders of magnitude within a very small interval of the effective thickness of an ultrathin film. The effective thickness at which the resistivity begins to fall is different for different film materials and for different substrate conditions, especially the substrate temperature. Among these factors, the fraction of the substrate surface area covered by the aggregates or islands or so-called particles would be very important from the point of view of the explanation of the phenomena by the theory of percolation. Neugebauer 1 displayed such a resistivity dependence on thickness of mercury films at various temperatures. Hill 2 also reported a series of papers specifically on the electrical conduction in ultrathin metal films. Among a number of investigators, Ambegaokar, Halperin, and Langer 3 employed a percolation approach to the conductivity dependence on temperature in a three-dimensional bulk disordered system of amorphous semiconductor and explained the T" 1/4 law of hopping conductivity very successfully. Pollak 4 further treated the dc conductivity by percolation theory and disParker (Ref. 10) for eV^> (2A*) indicates that, in fact, the excess quasiparticle density 6N can be determined from the measurement of the excess current in the plateau region. Furthermore, our analysis also shows that for an SIS tunnel junction with only one of the superconducting films being driven out of equilibrium, <5/ a -AA*6N and 6/ & -0 in the high-voltage limit. Therefore, without knowing whether one or both of the thin films are out of equilibrium, the total excess quasiparticle density determined from the plateau value of the excess current at eV ^ 2 A* can be off by a factor of 2, cussed cases including the T" 1/4 law and the activated conductivity. Attempting to perform a decisive experiment on the relation between percolation theory and electrical conductivity Last and Thouless 5 punched macroscopic holes in a sheet of colloidal graphite paper and measured its conductance. They claimed the conductivity behaved quite differently from the predictions of percolation theory. Their problem was later resolved by Kirkpatrick 6 as due to the differences between the percolation probability and the conductance of the sample. Watson and Leath 7 measured ...

The observed thickness dependence and excitation profiles of the surface-enhanced resonance Raman scattering (SERRS) from crystal violet (CV) on silver films demonstrated the importance of surface roughness and chemical effects. Using different normalization schemes in studying the excitation profile of SERRS we were able to identify that there are three multiplicative contributions to the observed overall enhancement, viz. the electromagnetic effect, the molecular resonance effect and the charge-transfer effect originating from the strong electronic interactions between CV and the metal islands.

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