title: Control of nitromethane photoionization efficiency with shaped femtosecond pulses.
abstract: The applicability of adaptive femtosecond pulse shaping is studied for achieving selectivity in the photoionization of low-density polyatomic targets. In particular, optimal dynamic discrimination (ODD) techniques exploit intermediate molecular electronic resonances that allow a significant increase in the photoionization efficiency of nitromethane with shaped near-infrared femtosecond pulses. The intensity bias typical of high-photon number, nonresonant ionization is accounted for by reference to a strictly intensity-dependent process. Closed-loop adaptive learning is then able to discover a pulse form that increases the ionization efficiency of nitromethane by ∼150%. The optimally induced molecular dynamics result from entry into a region of parameter space inaccessible with intensity-only control. Finally, the discovered pulse shape is demonstrated to interact with the molecular system in a coherent fashion as assessed from the asymmetry between the response to the optimal field and its time-reversed counterpart.
authors.affiliation: Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA. jroslund@princeton.edu
authors.forename: Jonathan
authors.initials: J
authors.lastname: Roslund
authors.forename: Ofer M
authors.initials: OM
authors.lastname: Shir
authors.forename: Arthur
authors.initials: A
authors.lastname: Dogariu
authors.forename: Richard
authors.initials: R
authors.lastname: Miles
authors.forename: Herschel
authors.initials: H
authors.lastname: Rabitz
mesh_terms: D000388:Air; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D009595:Nitroparaffins / Q000737:chemistry*; D055668:Photochemical Processes; D017785:Photons; D013997:Time Factors
chemical_list: D009595:Nitroparaffins; D008697:Methane; C008640:nitromethane