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Physical Sciences and Mathematics

Selected Works

Berwyck L. J. Poad

Coincidence

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Full-Text Articles in Social and Behavioral Sciences

Photoelectron-Photofragment Coincidence Studies Of No-_X Clusters (X = H2o, Cd4), Berwyck Poad, Christopher Johnson, Robert Continetti May 2013

Photoelectron-Photofragment Coincidence Studies Of No-_X Clusters (X = H2o, Cd4), Berwyck Poad, Christopher Johnson, Robert Continetti

Berwyck L. J. Poad

The dissociative photodetachment of NO -(H2O)and NO -(CD4) anion clusters was studied at 775 nm (1.60 eV) using photoelectron-photofragment coincidence spectroscopy. The correlation between the photoelectron and photodetached neutral spectra indicates vibrational excitation in the recoiling NO neutral fragments from NO-(H2O), with a progression consistent with vibrational excitation up to v(NO) = 3 in the products. The correlation remains when D2O is substituted for H2O, implying the NO vibrational mode plays a role in the dissociation coordinate of the complex. In contrast, no correlation was observed between photoelectron kinetic …


Photoelectron-Photofragment Coincidence Spectroscopy In A Cryogenically Cooled Linear Electrostatic Ion Beam Trap, Christopher J. Johnson, Ben B. Shen, Berwyck L. J Poad, Robert E. Continetti May 2013

Photoelectron-Photofragment Coincidence Spectroscopy In A Cryogenically Cooled Linear Electrostatic Ion Beam Trap, Christopher J. Johnson, Ben B. Shen, Berwyck L. J Poad, Robert E. Continetti

Berwyck L. J. Poad

A cryogenically cooled linear electrostatic ion beam trap for use in photoelectron-photofragment coincidence (PPC) spectroscopy is described. Using this instrument, anions created in cold, low-dutycycle sources can be stored for many seconds in a ∼20 K environment to cool radiatively, removing energetic uncertainties due to vibrationally excited precursor anions. This apparatus maintains a well-collimated beam necessary for high-resolution fragment imaging and the high experimental duty cycle needed for coincidence experiments. Ion oscillation is bunched and phase-locked to a modelocked laser, ensuring temporal overlap between ion bunches and laser pulses and that ions are intersected by the laser only when travelling …