# A Three-step Model of High Harmonic Generation using Complex Classical Trajectories

## TL;DR

This paper introduces a novel complex trajectory approach to high harmonic generation that unifies classically allowed and forbidden processes, providing a comprehensive dynamical framework for understanding strong field physics effects.

## Contribution

It presents a new trajectory formulation that models both allowed and forbidden processes in high harmonic generation within a single, seamless dynamical system.

## Key findings

- Complex trajectories orbit the nucleus, forming the Coulomb ground state.
- The model describes tunnel ionization, unbound evolution, and recollision seamlessly.
- The approach offers mechanistic insights into strong field physics phenomena.

## Abstract

We present a new trajectory formulation of high harmonic generation that treats classically allowed and classically forbidden processes within a single dynamical framework. Complex trajectories orbit the nucleus, producing the stationary Coulomb ground state. When the field is turned on, these complex trajectories continue their motion in the field-dressed Coulomb potential and therefore tunnel ionization, unbound evolution and recollision are described within a single, seamless framework. The new formulation can bring mechanistic understanding to a broad range of strong field physics effects.