Double-peak distribution of electron and ion emission profile during femtosecond laser ablation of metals

^a Istituto Nazionale per la Fisica della Materia (INFM), Unità di Napoli, Via Cintia 26, I-80126 Napoli, Italy

^b Dipartimento di Ingegneria e Fisica dell’Ambiente, Università della Basilicata, C.da Macchia Romana, I-85100 Potenza, Italy

^c Dipartimento di Scienze Fisiche, Università degli Studi di Napoli Federico II, Via Cintia 26, I-80126 Napoli, Italy

^d Dipartimento di Chimica, Università della Basilicata, C.da Macchia Romana, I-85100 Potenza, Italy

^e Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Via Cintia 26, I-80126 Napoli, Italy

Available online 31 October 2001.

Abstract

Femtosecond laser ablation of metals with a Ti:sapphire laser system has been investigated by a time-of-flight mass spectroscopy technique. Ion mass spectra show a double-peak distribution, evidencing the presence of a high-energy component (up to few keV), even at moderate laser intensities (10¹²–10¹³ W cm⁻²). Two different ablation regimes were identified for the less energetic component, and explained in the framework of the two-temperature modeling of ultrashort laser pulse–solid target interactions. Ambipolar diffusion has been identified as the probable mechanism giving rise to the observed high-energy plasma plume component.