SOFT X-RAYS TOMOGRAPHY

Thimble-Chamber Calibration on Soft X-rays

Condenser r-meter thimble chambers of various types have been calibrated against a standard free-air ionization chamber to indicate the wavelength dependance of their readings after exposure to X-rays excited by potentials ranging from 10 to 200 kilovolts. X-ray tubes with low inherent filtration are used. Calibrations are conducted for minimumfilter conditions, and the effect of added filtrati...

Probing nucleobase photoprotection with soft x-rays

Nucleobases absorb strongly in the ultraviolet region, leading to molecular excitation into reactive states. The molecules avoid the photoreactions by funnelling the electronic energy into less reactive states on an ultrafast timescale via non-BornOppenheimer dynamics. Current theory on the nucleobase thymine discusses two conflicting pathways for the photoprotective dynamics. We present our fi...

Employing Soft X-Rays in Experimental Astrochemistry

Soft X-rays from High-Velocity Clouds

The ROSATmission gave us the unique possibility to study the galactic interstellar medium by “shadowing” observations on arcmin angular resolution level. The high sensitivity of the ROSAT PSPC in combination with the large field of view allows the detailed study of individual clouds, while the ROSAT all-sky survey is the main source for studies of the large-scale intensity distribution of the d...

Soft x-ray microscopy with coherent x rays (invited)

The Soft X-ray Undulator beamline at the NSLS supports a soft x-ray imaging program including scanning transmission microscopy, scanning photoemission microscopy, Gabor and Fourier transform holography, and large angle diffraction. Zone plates from an LBL Center for X-ray Optics/IBM collaboration are used as optical elements. The current instrumentation of the beamline and the experimental stat...