RESUMO
Here, we report the coincident measurement of PICD and PECD effects in 1-phenylethylamine upon multiphoton ionization. Both photo-ion circular dichroism (PICD) and photo-electron circular dichroism (PECD) are methods to distinguish enantiomers. In PICD, a difference in total ion yields upon multiphoton ionization with circular polarized light is measured, whereas, in PECD, circular dichroism is observed in the angular distribution of the photoelectrons. Here, we report on our continuous effort to measure the PICD and PECD effects in coincidence, i.e. simultaneously under the same measurement conditions using a home-built photoion-photoelectron coincidence spectrometer. Pure samples of R-(+)-1-phenylethylamine and S-(-)-1-phenylethylamine have been photo-ionized using a femtosecond laser operated at 394 nm.
RESUMO
Two methods of laser-induced mass-selective chiral analysis based on circular dichroism have been reported in the literature: photo-ion circular dichroism (PICD) and photo-electron circular dichroism (PECD). In PICD, a difference in total ion yields upon multiphoton ionization with circular polarized light is measured, whereas in PECD, the circular dichroism is observed in the angular distribution of the photoelectrons. Here, we report the first coincident measurement of the PICD and PECD effects. A home-built photoion-photoelectron coincidence spectrometer has been used to measure both the PICD and the PECD effects simultaneously under the same measurement conditions. Pure samples of R- and S-methyloxirane have been photo-ionized using a femtosecond laser operation at 396 nm.
RESUMO
An accurate description of the interaction of intense hard X-ray pulses with heavy atoms, which is crucial for many applications of free-electron lasers, represents a hitherto unresolved challenge for theory because of the enormous number of electronic configurations and relativistic effects, which need to be taken into account. Here we report results on multiple ionization of xenon atoms by ultra-intense (about 1019 W/cm2) femtosecond X-ray pulses at photon energies from 5.5 to 8.3 keV and present a theoretical model capable of reproducing the experimental data in the entire energy range. Our analysis shows that the interplay of resonant and relativistic effects results in strongly structured charge state distributions, which reflect resonant positions of relativistically shifted electronic levels of highly charged ions created during the X-ray pulse. The theoretical approach described here provides a basis for accurate modeling of radiation damage in hard X-ray imaging experiments on targets with high-Z constituents.
