Modeling of the processes of ionization and excitation of nitrogen molecules by short and intense laser pulses

Abstract

We present a model describing ionization and excitation of nitrogen molecules by a strong and short laser pulse. In difference to previous publications, both processes are considered within the same formalism of density matrix. We account for the dependence of the dipole moment on the vibrational quantum number and for a large number of excited levels. Populations of the excited levels depend significantly on the laser intensity, wavelength, polarization and pulse duration.

Laser emission at 428 nm in N2+: Competition between two- and three-level amplification

“…1(b) and (c) for a schematic representation of the first two processes. Recent calculations show that population inversion between B0 and X0 is very sensitive to the particular pump pulse conditions 14,15 . B0/X0 inversion occurs if the pump central wavelength from a Ti:Sapphire laser exceeds 780 nm and if the pump intensity exceeds 1.5 × 10 14 W/cm 2 , but it disappears if one of these two values is decreased by less than 5%.…”

“…The difference by a factor of 3 in the intensities of fluorescence B0→X0 (391 nm) and B0→X1 (428 nm) is explained by the corresponding difference in the Einstein coefficients (see Ref. 14 , Tab. 1).…”