Can quantum control help us build coherent spectroscopies involving continua?

Advanced x-ray sources capable of creating bright, directed laser beams in the xuv and x-ray regions allow for probing the electronic and structural changes that govern a broad range of atomic and molecular processes. Applications so far relied on the short pulse duration, high intensity, and broad frequency coverage of ultrafast x-rays but their high degree of coherence has not yet been utilized. The latter should allow for performing non-linear x-ray spectroscopies such as coherent Raman excitation. A key prerequisite is, however, the ability to suppress losses such as ionization that are due to the presence of a continuum.

I will discuss the opportunities and limitations for coherent control of processes that involve a continuum, taking photoassociation as an example. In photoassociation a bond is formed between two scattering atoms upon laser excitation. I will discuss the implications of the continuum structure on control. I will then explain how optimal control theory can be combined with state of the art tools to describe electron dynamics and present optimal control results for a model of x-ray Raman excitation in neon.