THE STRUCTURE OF PHOTOEXCITED PLATINUM POP MEASURED WITH MICROSECOND RESOLVED XAFS

We report a musec resolved XAFS measurement of the excited triplet ele ctronic state 3A2u(dsigmapsigma) of Pt2(P2O5H2)44- in solution employ ing a new technique. The measurement utilizes a vertical flow of 10 m/ s produced by a small nozzle, similiar to that of a dye laser. A line focused laser excites the molecules in the flow while a 10 mum vertica lly confined line of x-ray radiation probes the flow downstream of the laser. We find that the phosphor planes of the molecule in the excite d state each move inward along the Pt-Pt axis by 0.26(08) angstrom, re lative to its the center. Also, the platinum phosphorous bonds contrac t 0.050(11) angstrom. The optical transition promotes an electron from an anti-bonding orbital to a bonding orbital, and the observations in dicate that this occupied bonding orbital strongly increases the overa ll structural bonding forces of the molecule.