Multiple ionisation and Coulomb explosion in terawatt photoexcitation of Xenon clusters: An experimental and theoretical study

Abstract

Multiple ionisation and Coulomb explosion following photoexcitation of xenon clusters has been studied at ∼1012 W/cm2 at three different wavelengths in UV and visible region. Multiply charged xenon ions (Xen+) up to +4, +6 and +10 states were observed in time-of-flight mass spectra at 266, 355 and 532 nm respectively. Energetic electrons were also detected and electron energy distribution was measured at all the three wavelengths. The maximum electron energy was found to be dependent on the ionising wavelength. It has been established that multiphoton ionisation creates Xe+ ions and the energised electrons cause secondary ionization of singly charged xenon ion (Xe+) to give rise to higher charged states of xenon. An analytical model has been developed to understand the multiple ionization of xenon clusters at terawatt laser intensity. It reveals that lowering of ionization potential and excitation to Rydberg states of ions are important factors to generate high charge states like Xe10+commensurate with the experimental results.