Enhancement of Kα emission through efficient hot electron generation in carbon nanotubes on intense laser pulse irradiation

Abstract

Near complete absorption of the energy of intense ultra-short laser pulses (45 fs, intensity ∼1.6 × 1016 to 2.5 × 1017 W/cm2) is observed in carbon nanotubes deposited on a planar molybdenum substrate. The hollow structure of the nanotube plasma facilitates resonant electric field enhancement during its ionization phase. This resonantly enhanced localized field at a density much larger than the critical density nc leads to efficient hot electron generation, which results in enhanced Kα emission of Mo at 17.5 keV. It is observed that for nanotubes, depending on the degree of hollowness, there is an optimum laser intensity for maximum x-ray enhancement compared to a planar uncoated target.