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Tunable far-infrared laser vibration-rotation-tunnelling spectroscopy (FIRVRTS) has been used to measure several intermolecular vibrations in the water trimer. Together with ab initio and group theoretical results, these data characterize the structure and especially the tunnelling dynamics of this system in considerable detail.

Abstract:The LCLS hard x-ray Free Electron Laser at SLAC reported first lasing in April of 2009. Since then two successful user runs have been completed at the two soft x-ray stations. The first hard x-ray station has started commissioning in July of 2010. Beam diagnostics play an essential role for tuning the machine and delivering the requested beam properties to the users. An overview of the LCLS photon diagnostics will be presented including some selected commissioning results. Plans for future improvements and upgrades will be briefly discussed.

The capabilities of a step-scan Fourier transform spectrometer of obtaining time-resolved spectra are reported. As a demonstration of the method, time-resolved spectra from a pulsed fluorescent lamp are presented. The potential of step-scan interferometry for time-resolved infrared measurements of a variety of transient phenomena is discussed.

Laser-assisted chemical vapor deposition (LCVD) was utilized to produce SnO 2 films from SnBr 4 plus air, O 2 or N 2 O. SnO 2 films were successfully generated using either 222 or 308 nm laser pulses but there was evidence for film contamination when using less than 60 mJ/ pulse laser energies at 222 nm. Films were characterized using ultraviolet absorption spectroscopy; the spectra of films with impurities resembled the spectrum of SnBr 4 . AFM images were obtained which indicated that this LCVD route produced small and fairly uniform SnO 2 grains which were 50-100 nm in size. Multiphoton ionization spectroscopy was used to verify that the dissociation of a film dopant precursor, copper(II) acetate, produced gasphase copper atoms under conditions similar to those used in film deposition experiments. The deposition of SnO 2 from SnBr 4 plus an oxidant was found to be more efficient than from di-nbutyl tin diacetate but films produced via this new LCVD route, including those doped with copper, were found to be much less sensitive in preliminary gas-sensing screening.

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