Abstract

High-intensity femtosecond (fs) light pulses provide the means to excite, on a subpicosecond time scale, the electrons in a solid to temperatures T_e greatly in excess of the lattice vibrational temperature T_l.^[1] As shown in an earlier experiment on Ag,^[2] for excitation of the electron gas to temperatures kT_e approaching ϕ (ϕ is the workfunction of the metal), subpicosecond thermionic emission supersedes multiphoton photoemissioni^[3] as the major electron-emission process and is thus a candidate for evaluating the temperature T_e under intense fs radiation. However, the space-charge potential associated with the emitted electron packet, in addition to limiting the total emitted yield, distorts the measured distribution from its initial thermal character. Here we achieve semiquantitative assessment of the yield and distributions by measuring, in combination, the incident-light reflectivity, the total electron yield, and electron-energy distributions curves (EDC’s) of the emitted electrons from three very different single-crystal surfaces—Ag, Al, and W—under UHV conditions. A simple quasi-one-dimensional (ID) analytical model and a more rigorous quasi-two-dimensional (2D) particle in a cell (PIC) simulation have been developed to understand the measured yield and EDC’s.

© 1992 The Author(s)