Ultrafast transient dynamics of adsorbates on surfaces deciphered: The case of CO on Cu(100)

Time-resolved vibrational spectroscopy constitutes an invaluable experimental tool for monitoring hotcarrier-induced surface reactions. However, the absence of a full understanding of the precise microscopic mechanisms causing the transient spectral changes has limited its applicability. Here we introduce a robust first-principles theoretical framework that successfully explains both the nonthermal frequency and linewidth changes of the CO internal stretch mode on Cu(100) induced by femtosecond laser pulses. Two distinct processes engender the changes: electron-hole pair excitations underlie the nonthermal frequency shifts, while electron-mediated vibrational mode coupling gives rise to linewidth changes. Furthermore, the origin and precise sequence of coupling events are finally identified.D. N. acknowledges financial support from the European Regional Development Fund for the “Center of Excellence for Advanced Materials and Sensing Devices” (Grant No. KK.01.1.1.01.0001) as well as from Donostia International Physics Center (DIPC). J. C. T. is grateful to the Deutsche Forschungsmeinschaft for funding through Grant No. TR1109/2-1. M. A. and J. I. J. acknowledge the Spanish Ministerio de Economía, Industria y Competitividad Grant No. FIS2016-76471-P.Peer reviewe