title: Imaging Electronic Excitation of NO by Ultrafast Laser Tunneling Ionization.
abstract: Tunneling-ionization imaging of photoexcitation of NO has been demonstrated by using few-cycle near-infrared intense laser pulses (8 fs, 800 nm, 1.1×10^{14}  W/cm^{2}). The ion image of N^{+} fragment ions produced by dissociative ionization of NO in the ground state, NO (X^{2}Π,2π)→NO^{+}+e^{-}→N^{+}+O+e^{-}, exhibits a characteristic momentum distribution peaked at 45° with respect to the laser polarization direction. On the other hand, a broad distribution centered at ∼0° appears when the A^{2}Σ^{+} (3sσ) excited state is prepared as the initial state by deep-UV photoexcitation. The observed angular distributions are in good agreement with the corresponding theoretical tunneling ionization yields, showing that the fragment anisotropy reflects changes of the highest-occupied molecular orbital by photoexcitation.
authors.affiliation: Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi 464-8602, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Endo
authors.affiliation: Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi 464-8602, Japan.
authors.forename: Akitaka
authors.initials: A
authors.lastname: Matsuda
authors.affiliation: Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi 464-8602, Japan.
authors.forename: Mizuho
authors.initials: M
authors.lastname: Fushitani
authors.affiliation: The Open University of Japan, Mihama, Chiba 261-8586, Japan.
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Yasuike
authors.affiliation: Moscow Institute of Physics and Technology, Dolgoprudny 141700, Russia.
authors.forename: Oleg I
authors.initials: OI
authors.lastname: Tolstikhin
authors.affiliation: Institute for Advanced Science, The University of Electro-Communications, 1-5-1 Chofu-ga-oka, Chofu, Tokyo 182-8585, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Morishita
authors.affiliation: Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi 464-8602, Japan.
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Hishikawa