Multi-peaked photoelectron energy spectrum in resonant two-photon ionisation

R I Jackson, Dennis P. O’Brien, S. Swain

R I Jackson, D P O'Brien, S. Swain

The authors investigate two-photon ionisation using a generalised rate equation technique for a model in which the atom is assumed to have only two bound levels (the ground state and an excited state) together with a simple continuum of ionised states. Spontaneous emission is allowed from the excited to the ground state, and the laser is assumed to have a finite bandwidth due to phase diffusion. The photoelectron energy distribution is calculated; it is found that if the Rabi frequency exceeds the ionisation rate the energy spectrum is a sensitive function of the linewidth and spontaneous emission rate, whereas if the ionisation rate exceeds the Rabi frequency then the sensitivity of the energy spectrum to these parameters depends upon the initial state of the system. A quite small value of laser linewidth is found to considerably reduce the heights of peaks and increase the widths. Analytic and numerical results are presented.

S. N. Dixit

L Armstrong, Stephen V. O'Neil

The authors study the resonance lineshape in two-photon ionisation of atoms when the power broadening due to the bound-bound transitions is by far the dominant broadening mechanism. The authors consider the effect on the lineshape of turn-on of the laser-atom interaction, spontaneous emission and laser linewidth, and show that several different types of lineshapes can result depending on the conditions involved. The authors also consider the photoelectron spectrum, and show that it is also sensitive to these same parameters.

R. Parzyński

P. L. Knight

Autler-Townes splitting of photoelectron energy distributions in resonant two-photon ionisation is predicted using standard Heitler-Ma techniques.