Adiabatic passage to the continuum

TL;DR

This paper shows how changing the chirp direction in VUV pulses can control excitation or ionization with high contrast by leveraging adiabatic passage to the continuum, involving interference effects between bound states.

Contribution

It extends the concept of rapid adiabatic passage to include transitions to the continuum, demonstrating control over ionization via chirp phase manipulation.

Findings

Chirp direction determines whether excitation or ionization occurs.

Interference between bound states can be controlled by the chirp phase.

Effect verified through minimal model and helium calculations.

Abstract

We demonstrate that by changing the direction of the chirp in VUV pulses one can switch between excitation and ionization with very high contrast, if the carrier frequency of the light is resonant with two bound states. This is a surprising consequence if rapid adiabatic passage is extended to include transitions to the continuum. The chirp phase locks the linear combination of two resonantly coupled bound states whose ionization amplitudes interfere constructively or destructively depending on the chirp direction under suitable conditions. We derive the phenomenon in a minimal model and verify the effect with calculations for helium as a realistic example.