Picosecond calorimetry: Time-resolved x-ray diffraction studies of liquid CH2Cl2

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Panayiotis Georgiou, Jonathan Vincent, Magnus Andersson, Annemarie B. Wöhri, Pontus Emanuel Gourdon, Jens Poulsen, Jan Davidsson, Richard Neutze

Liquid phase time-resolved x-ray diffraction with 100 ps resolution has recently emerged as a powerful technique for probing the structural dynamics of transient photochemical species in solution. It is intrinsic to the method, however, that a structural signal is observed not only from the photochemical of interest but also from the embedding solvent matrix. To experimentally characterize the x-ray diffraction signal deriving from the solvent alone we performed time-resolved diffraction studies of a pure liquid sample over a time domain from -250 ps to 2.5 μs. Multiphoton excitation was used to rapidly heat liquid C H2 Cl2 using UV pulses of 100 fs duration. A significant x-ray diffraction signal is visible prior to the onset of thermal expansion, which characterizes a highly compressed superheated liquid. Liquid C H2 Cl2 then expands as a shock wave propagates through the sample and the temporal dependence of this phenomenon is in good agreement with theory. An unexpectedly slow initial release of energy into the liquid as heat is observed from multiphoton excited C H2 Cl2, revealing the presence of a metastable state of multiphoton excited C H2 Cl2.

Original languageEnglish
Article number234507
JournalJournal of Chemical Physics
Volume124
Issue number23
ISSN0021-9606
DOIs
Publication statusPublished - 21 Jun 2006

ID: 126104012