ABSTRACT
A photoelectron-photofragment coincidence (PPC) study of the dissociative photodetachment of OHF at a photon energy of 4.80 eV is presented. The correlated electron kinetic energy (eKE) and translational energy release (E(T)) into the O + HF + e- products yield information on the potential energy surface close to the transition state of the neutral reaction OH + F --> O + HF. The correlation spectrum shows two different features in the energetically allowed O + HF product channel: (a) diagonal ridges, resulting from direct dissociative photodetachment (DPD) and (b) areas with higher E(T) in the neutral fragments from nonadiabatic dissociation. The total translational energy spectrum (E(TOT) = eKE + ET) reveals a vibrationally resolved product state distribution. These results are discussed in the context of recent theoretical studies of the dissociative photodetachment of OHF-.
Subject(s)
Fluorides/chemistry , Hydrofluoric Acid/chemistry , Hydroxides/chemistry , Oxygen/chemistry , Electrons , Energy Transfer , Kinetics , PhotochemistryABSTRACT
The polarization control method offers a flexible, robust, and low-cost route for the parallel fabrication of gratings with complex apodization profiles including several discrete phase shifts and chirp. The performance of several test gratings is evaluated in terms of their spectral response and compared with theoretical predictions. Short gratings with sidelobe-suppression levels in excess of 32 dB and transmission dips lower than 80 dB have been realized. Finally, most of the devices fabricated by the polarization control method show comparable quality to gratings manufactured by far more complex methods.
ABSTRACT
We demonstrate a new class of hollow-core Bragg fibers that are composed of concentric cylindrical silica rings separated by nanoscale support bridges. We theoretically predict and experimentally observe hollow-core confinement over an octave frequency range. The bandwidth of bandgap guiding in this new class of Bragg fibers exceeds that of other hollow-core fibers reported in the literature. With only three rings of silica cladding layers, these Bragg fibers achieve propagation loss of the order of 1 dB/m.
