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1992

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All HMC Faculty Publications and Research

Articles 1 - 4 of 4

Full-Text Articles in Physics

Direct Picosecond Measurement Of Photoinduced Cooper Pair Breaking In Lead, John F. Federici, Benjamin I. Greene, Peter N. Saeta, Douglas R. Dykaar, F. Sharifi, R. C. Dynes Nov 1992

Direct Picosecond Measurement Of Photoinduced Cooper Pair Breaking In Lead, John F. Federici, Benjamin I. Greene, Peter N. Saeta, Douglas R. Dykaar, F. Sharifi, R. C. Dynes

All HMC Faculty Publications and Research

We report on a direct kinetic measurement of Cooper-pair breaking in superconducting lead. A 100-fs pulse of visible light was used to excite a thin-film lead sample, while the Cooper-pair density was optically probed using an ultrashort pulse of broadband far-infrared radiation. Subsequent to the absorption of the visible light, a rapid (ps) change in the far-infrared optical transmission was observed, corresponding to the breaking of Cooper pairs and the collapse of the superconducting gap.

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A Theoretical Investigation Of The Ground And Low‐Lying Excited States Of Butadiene Radical Cation, Robert J. Cave, Michael G. Perrott '90 Mar 1992

A Theoretical Investigation Of The Ground And Low‐Lying Excited States Of Butadiene Radical Cation, Robert J. Cave, Michael G. Perrott '90

All HMC Faculty Publications and Research

Results are presented from ab initio calculations on the ground and several low‐lying excited states of the butadiene radical cation. In particular, we have calculated geometries for the ground and several excited states at the multiconfiguration self‐consistent field level and characterized the planar stationary points. The vertical ionization potentials from the neutral molecule ground state and vertical excitation energies at the computed equilibrium geometry of the cation were also examined. A variety of methods were tested for the calculation of ionization potentials and excitation energies, including multiconfiguration self‐consistent field, multireference singles and doubles configuration interaction (with and without size‐consistency correction), …

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Intervalley Scattering In Gaas And Inp Probed By Pulsed Far‐Infrared Transmission Spectroscopy, Peter N. Saeta, John F. Federici, Benjamin I. Greene, Douglas R. Dykaar Mar 1992

Intervalley Scattering In Gaas And Inp Probed By Pulsed Far‐Infrared Transmission Spectroscopy, Peter N. Saeta, John F. Federici, Benjamin I. Greene, Douglas R. Dykaar

All HMC Faculty Publications and Research

The dynamics of photoexcited electrons in GaAs and InP were studied using the transmission of 200‐fs pulses of far‐infrared radiation in the spectral range 15–100 cm−1. Kinetic traces of the infrared transmission as a function of delay between optical excitation and infrared probe show a probe‐limited decrease in transmission followed by a more gradual (0.7–2 ps) drop to a steady value, consistent with the slow return of electrons from high‐mass satellite valleys. Infrared transmission spectra, analyzed in the context of a Drude model, reveal density‐dependent electron mobilities 3–4 times below equilibrium n‐doped values. Electron‐hole collisions likely account …

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Optical Rectification At Semiconductor Surfaces, Shun Lien Chuang, Stefan Schmitt-Rink, Benjamin I. Greene, Peter N. Saeta, Anthony F. J. Levi Jan 1992

Optical Rectification At Semiconductor Surfaces, Shun Lien Chuang, Stefan Schmitt-Rink, Benjamin I. Greene, Peter N. Saeta, Anthony F. J. Levi

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We show that far-infrared radiation can be generated in the depletion field near semiconductor surfaces via the inverse Franz-Keldysh effect or electric-field-induced optical rectification. This mechanism is conceptually different from those previously proposed and accounts for many recent experimental observations.

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