Asymmetric effect of slowly varying chirped laser pulses on the adiabatic state exchange of a molecule

Here we show that the adiabatic theorem, originally derived for bound molecular systems, does not necessarily hold for dissociative molecular systems. In particular, we demonstrate here the asymmetric adiabatic evolution of the vibrational states of H + 2 under the influence of slowly varying chirped laser pulses. There are some laser parameters for which non-Hermitian degeneracies occur in the spectrum of the problem. These are known as exceptional points. When one slowly cycles the laser intensity and wavelength in a loop in parameter space around an exceptional point, the initial tenth vibrational state of H + 2 flips into the ninth vibrational state by the end of the loop. However, within the same excursion around an exceptional point in the laser parameters space, the ninth vibrational state of H + 2 does not flip into the tenth vibrational state but winds up unchanged by the end of the loop.