RESUMO
We report x-ray free electron laser experiments addressing ground-state structural dynamics of the diplatinum anion Pt_{2}POP_{4} following photoexcitation. The structural dynamics are tracked with <100 fs time resolution by x-ray scattering, utilizing the anisotropic component to suppress contributions from the bulk solvent. The x-ray data exhibit a strong oscillatory component with period 0.28 ps and decay time 2.2 ps, and structural analysis of the difference signal directly shows this as arising from ground-state dynamics along the PtPt coordinate. These results are compared with multiscale Born-Oppenheimer molecular dynamics simulations and demonstrate how off-resonance excitation can be used to prepare a vibrationally cold excited-state population complemented by a structure-dependent depletion of the ground-state population which subsequently evolves in time, allowing direct tracking of ground-state structural dynamics.
RESUMO
'Nowhere in pathology has a chaos of names so clouded clear concepts as in the subject lymphoid tumors'. R.A. Willis. In 1858, Rudolf Virchow, with a primitive microscope and limited experiential base, recognized 'at least three different conditions here, hyperinosis, leucocytosis and leukemia .'. One hundred and fifty years later, the World Health Organization (WHO 2008), with a much more extensive armamentarium of tools, and a wealth of diverse experience, promulgated criteria distinguishing more than 100 types of 'Tumors of the Hematopoietic and Lymphoid Tissues'. From three to one hundred and three; this is progress! And this is history! Our goal is to examine the course and causes of this history; how we moved from three entities to a hundred and three, what we have learned from it, and how we may use the insights that we have gained to anticipate 'future histories' in this marvelously dynamic area of biology and disease.
