Multiple ionisation of atom clusters by intense soft X-rays from a free-electron laser

Sem informaçãoIntense radiation from lasers has opened up many new areas of research in physics and chemistry, and has revolutionized optical technology. So far, most work in the field of nonlinear processes has been restricted to infrared, visible and ultraviolet light(1), although progress in the development of X-ray lasers has been made recently(2). With the advent of a free-electron laser in the soft-X-ray regime below 100 nm wavelength(3), a new light source is now available for experiments with intense, short-wavelength radiation that could be used to obtain deeper insights into the structure of matter. Other free-electron sources with even shorter wavelengths are planned for the future. Here we present initial results from a study of the interaction of soft X-ray radiation, generated by a free-electron laser, with Xe atoms and clusters. We find that, whereas Xe atoms become only singly ionized by the absorption of single photons, absorption in clusters is strongly enhanced. On average, each atom in large clusters absorbs up to 400 eV, corresponding to 30 photons. We suggest that the clusters are heated up and electrons are emitted after acquiring sufficient energy. The clusters finally disintegrate completely by Coulomb explosion.Intense radiation from lasers has opened up many new areas of research in physics and chemistry, and has revolutionized optical technology. So far, most work in the field of nonlinear processes has been restricted to infrared, visible and ultraviolet light(1), although progress in the development of X-ray lasers has been made recently(2). With the advent of a free-electron laser in the soft-X-ray regime below 100 nm wavelength(3), a new light source is now available for experiments with intense, short-wavelength radiation that could be used to obtain deeper insights into the structure of matter. Other free-electron sources with even shorter wavelengths are planned for the future. Here we present initial results from a study of the interaction of soft X-ray radiation, generated by a free-electron laser, with Xe atoms and clusters. We find that, whereas Xe atoms become only singly ionized by the absorption of single photons, absorption in clusters is strongly enhanced. On average, each atom in large clusters absorbs up to 400 eV, corresponding to 30 photons. We suggest that the clusters are heated up and electrons are emitted after acquiring sufficient energy. The clusters finally disintegrate completely by Coulomb explosion.4206915482485Sem informaçãoSem informaçãoSem informaçãoWe thank the TTF team at DESY, especially P. Castro, M. Minty, D. Nölle, H. Schlarb and S. Schreiber, for running the accelerator; we also thank J. R. Schneider for support and discussions. The first group of authors (H.W. to T.M.) built the apparatus for the cluster experiment and performed the experiment; the second group of authors (B.F. to M.Y) worked on the FEL and the diagnostics. We thank K.H. Meiwes-Broer, T. Brabec, C. Rose-Petruck, J. Krzywinski, M. Lezius, I. Kostyukov, J.M. Rost, E. Ru¨hl, U. Saalman, J. Jortner and M. Smirnov and their research groups for discussions and comments, and J. Sutter for critically reading the manuscript. This work was supported by the DFG

Moving in or Breaking Up? The Role of Distance in the Development of Romantic Relationships

Most romantic relationships start with a living apart together (LAT) phase during which the partners live in two separate households. Over time, a couple might decide to move in together, to separate, or to remain together while maintaining their nonresidential status. This study investigates the competing risks that partners in a LAT relationship will experience the transition to coresidence or to separation. We consider the amount of time LAT partners have to travel to see each other to be a key determinant of relationship development. For our statistical analyses, we use seven waves of the German Family Panel Pairfam (2008/2009-2014/2015) and analyze couples in the age group 20-40 years. We distinguish between short-distance relationships (the partners have to travel less than one hour) and long-distance relationships (the partners have to travel one hour or more). Estimating a competing risks model, we find that couples in long-distance relationships are more likely to separate than those living in close proximity. By contrast, the probability of experiencing a transition to coresidence is lower for LAT couples in long-distance than for those in short-distance relationships. Interaction analyses reveal that distance seems to be irrelevant for the relationship development of couples with two nonemployed (unemployed, in education or other inactive) partners