Time-Resolved Femtosecond Laser-Induced Desorption from Magnesium Oxide and Lithium Fluoride Single Crystals

Journal Article · Wed Dec 01 04:00:00 EST 1999 · Surface Science

OSTI ID:15001371

Beck, Kenneth M ^[1]; Joly, Alan G ^[1]; Hess, Wayne P ^[1]

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1. BATTELLE (PACIFIC NW LAB)

We have used the pump-probe technique to measure the photostimulated positive ion yield, as a function of time-delay between two sub-threshold femtosecond laser pulses. We find the ion yield, from 265 nm femtosecond irradiated MgO and LiF, depends critically on the laser pulse delay two-pulse experiments. For example, single pulse excitation of MgO produces a variety of ions including Mg+, MgO+, and H+. If the femtosecond laser pulse is split into two sub-threshold beams and then re-combined with a variable time delay, the Mg+ desorption yield displays three distinct lifetimes and persists for laser delays of over 100 picoseconds. A pulse delay of only 500 femtoseconds nearly eliminates ion desorption except for Mg+. In contrast, for LiF the majority of Li+ yields decays rapidly, largely within the femtosecond pulse duration. However, a weak but measurable decay component of approximately 2 picoseconds is indicated. We hypothesize the nonresonant two-photon excitation contributes to the ultrafast desorption mechanism through the creation of electron/hole pairs and allows direct observation of the surface electron/hole pair trapping dynamics and measurement of the surface free carrier lifetime.

• Research Organization: Pacific Northwest National Lab., Richland, WA (US)
• Sponsoring Organization: US Department of Energy (US)
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 15001371
• Report Number(s): PNNL-SA-33218; KC0301020
• Journal Information: Surface Science, Journal Name: Surface Science Journal Issue: 1-3 Vol. 451
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
CARRIER LIFETIME
DESORPTION
EXCITATION
LASER RADIATION
LITHIUM FLUORIDES
MAGNESIUM OXIDES
PULSE TECHNIQUES
RADIATION EFFECTS
TIME DELAY