PT  - JOURNAL ARTICLE
AU  - Ferguson, Ken R.
AU  - Bucher, Maximilian
AU  - Gorkhover, Tais
AU  - Boutet, Sébastien
AU  - Fukuzawa, Hironobu
AU  - Koglin, Jason E.
AU  - Kumagai, Yoshiaki
AU  - Lutman, Alberto
AU  - Marinelli, Agostino
AU  - Messerschmidt, Marc
AU  - Nagaya, Kiyonobu
AU  - Turner, Jim
AU  - Ueda, Kiyoshi
AU  - Williams, Garth J.
AU  - Bucksbaum, Philip H.
AU  - Bostedt, Christoph
TI  - Transient lattice contraction in the solid-to-plasma transition
AID  - 10.1126/sciadv.1500837
DP  - 2016 Jan 01
TA  - Science Advances
PG  - e1500837
VI  - 2
IP  - 1
4099  - http://advances.sciencemag.org/content/2/1/e1500837.short
4100  - http://advances.sciencemag.org/content/2/1/e1500837.full
SO  - Sci Adv2016 Jan 01; 2
AB  - In condensed matter systems, strong optical excitations can induce phonon-driven processes that alter their mechanical properties. We report on a new phenomenon where a massive electronic excitation induces a collective change in the bond character that leads to transient lattice contraction. Single large van der Waals clusters were isochorically heated to a nanoplasma state with an intense 10-fs x-ray (pump) pulse. The structural evolution of the nanoplasma was probed with a second intense x-ray (probe) pulse, showing systematic contraction stemming from electron delocalization during the solid-to-plasma transition. These findings are relevant for any material in extreme conditions ranging from the time evolution of warm or hot dense matter to ultrafast imaging with intense x-ray pulses or, more generally, any situation that involves a condensed matter-to-plasma transition.