Improved two-temperature model including electron density of states effect for Ni during femtosecond laser pulses

Abstract

Electron-phonon coupling factor and electron heat capacity based on the electron density of states are investigated for transition metal Ni under femtosecond laser irradiation. The thermal excitation of d band electrons is found to result in large deviations from the commonly used approximations of linear temperature dependence of the electron heat capacity and the constant electron-phonon coupling factor. Results of the simulations performed with the two-temperature model demonstrate that the electron-phonon relaxation time becomes long for high fluence laser for Ni. The satisfactory agreement between our numerical results and experimental data of threshold fluence indicates that the electron temperature dependence of the thermophysical parameters accounting for the thermal excitation of d band electrons should not be neglected under the condition that electron temperature is higher than 10⁴ K.