Rhiannon Porter

Coherent anti-Stokes Raman scattering microscopy with spectrally tailored ultrafast pulses

We report a coherenti-Stokes Raman scattering (CARS) microscopy method using tailored ultrafast pulses from a broadband chirped-pulse-amplification Ti: Sapphire laser. Three input waves were obtained at the pulse compressing stage. An air-spaced etalon was used to generate the narrow band waves (2ω1), and a hard aperture mask was used to produce the broadband wave (ω2). Spectral resolution as high as 7cm−1 can be achieved with the etalon, and the temporal resolution was ∼1 picosecond. Two-dimensional (2D) time-resolved vibrational CARS spectrographs covering 820–1500cm−1 were obtained from opaque and transparent thin films.

Silicon-based nanowires from silicon wafers catalyzed by cobalt nanoparticles in a hydrogen environment

We present here the synthesis of silicon-based nanowires directly from silicon wafers at high temperatures and in the presence of cobalt nanoparticles and hydrogen gas. All three ingredients were critical to the growth of Si-based nanowires, which were between 5-60 nm in diameter and microm-mm long. Both heavily coiled and straight Si-based nanowires were made. Experimental evidence suggested that the sources of silicon for the nanowires growth were in the gas phase.

Imaging Plume Dynamics with Ultrafast Hard X-rays

Results on plume dynamics of laser ablation of metal films in helium at ambient pressure studied with ultrafast hard x-ray imaging are presented. The speed of the x-ray absorbing plume was measured at 1×102 m/sec.

More Power to X-Rays: From Ultrafast Dynamics of Metal Complexes to Enhanced Damage to DNA

X-ray spectroscopy was used to investigate charge transfer and subsequent events such as structural rearrangement and radical generation in metal complexes including metal nanoparticles. Several new phenomena were observed and the accompanying mechanisms were investigated.

Investigation of Plume Dynamics with Ultrafast Hard X-Ray Absorption Spectroscopy

Results on plume dynamics of pulsed laser ablation of metal thin films in helium at ambient pressure studied with ultrafast hard x-ray absorption spectroscopy/imaging are presented. The x-ray absorbing plume propagated at 4x102 m/sec.