title: Space-time contours to treat intense field-dressed molecular states. I. Theory.
abstract: A molecular system exposed to an intense external field is considered. The strength of the field is measured by the number L of electronic states that become populated during this process. In the present article the authors discuss a rigorous way, based on the recently introduced space-time contours [R. Baer, et al., J. Chem. Phys. 119, 6998 (2003)], to form N coupled Schrodinger equations where N<L, which maintains the effects due to the remaining (L-N) populated states. It is shown that whereas the size of L is unlimited, the main requirement concerning N is that the original group of N field-free states forms a Hilbert subspace in the spatial region of interest. From previous studies it is known that a group of states forms a Hilbert subspace if and only if the corresponding topological D matrix is diagonal [M. Baer, et al., Farad, Discuss 127, 337 (2004)].
authors.affiliation: Department of Chemistry, Indian Institute of Technology, Guwahati, North Guwahati, Guwahati 781039, India.
authors.forename: Biplab
authors.initials: B
authors.lastname: Sarkar
authors.forename: Satrajit
authors.initials: S
authors.lastname: Adhikari
authors.forename: Michael
authors.initials: M
authors.lastname: Baer