We analyze the propagation of a wave packet through a conical intersection. This
question was addressed for Gaussian wave packets in the 90s by George Hagedorn
and we consider here a more general setting. We focus on the case of the
Schrödinger equation but our methods are general enough to be adapted to systems
presenting codimension-2 crossings and to codimension-3 ones with specific geometric
conditions. Our main theorem gives explicit transition formulas for the profiles when
passing through a conical crossing point, including precise computation of the
transformation of the phase. Its proof is based on a normal form approach combined
with the use of superadiabatic projectors and the analysis of their degeneracy close to
the crossing.
Dedicated to the memory of George
Hagedorn (1953–2023)