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O: Fachverband Oberflächenphysik
O 60: Time-Resolved Spectroscopies
O 60.5: Talk
Thursday, March 29, 2007, 16:45–17:00, H42
Ultrafast Vibrational Dynamics of CO/Ir(111) — •Heike Arnolds, Ian Lane, and David King — Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
We present a set of experiments that provide a complete mapping of coherent and incoherent vibrational relaxation times for a saturated layer of CO on a metal surface, Ir(111). Using femtosecond infrared pump - sum frequency probe spectroscopy, we measure the vibrational spectrum, the free induction decay and the vibrational lifetime. We also present the first measurement of a mid-infrared photon echo from a metallic surface, some fifteen years after the analogous measurement on a semiconductor surface. We find that the spectral linewidth (∼5 cm−1) in this strongly dipole-coupled system is dominated by lifetime broadening and inhomogeneity, with only a small contribution from pure homogeneous dephasing due to coupling with low frequency modes. In addition, we see a change in echo peak shape with delay time, which shows that the inhomogeneity in this system is not static, instead frequency fluctuations contribute on different time scales.