AVS 49th International Symposium
    Surface Science Tuesday Sessions
       Session SS1-TuA

Paper SS1-TuA4
Time Resolved Femtosecond Laser Desorption from Ionic Crystals

Tuesday, November 5, 2002, 3:00 pm, Room C-108

Session: Ultrafast Phenomena & Dynamics at Surfaces
Presenter: W.P. Hess, Pacific Northwest National Laboratory
Authors: W.P. Hess, Pacific Northwest National Laboratory
A.G. Joly, Pacific Northwest National Laboratory
K.M. Beck, Pacific Northwest National Laboratory
J.T. Dickinson, Washington State University
Correspondent: Click to Email
We have used femtosecond laser pulse pairs to measure the positive ion yield, from wide band-gap single crystals, as a function of time-delay between pulses. The two-pulse technique allows direct observation of solid state and surface dynamics on a femtosecond timescale. We find the ion yield, from 265 nm irradiated MgO, KBr, and LiF, depends critically on the time delay between pulses. For example, the Mg+ desorption yield displays three distinct features; a coherence peak, followed by rise, and decay features. In contrast, the yield of K+ and Li+ from KBr and LiF display only the coherence peak and picosecond decay features. The observed thresholds suggest, that although the ion desorption mechanism is dominated by defect photoabsorption, significant electron-hole pair production may contribute to the desorption mechanism following femtosecond excitation. The picosecond lifetimes correspond well with known electron-hole lifetimes in each material. We hypothesize that fs laser desorption may be related to the creation of electron hole pairs. By determining the ultrafast time-dependence we hope to reveal details of the ion desorption mechanism.