ID: 61 Coincidence imaging study on (e,2e) reaction dynamics of H2 at large momentum transfer M. Takahashi; 1; 1. Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, Japan. Abstract Body: An electron-impact ionizing collision in which the momenta of the incident and two outgoing electrons are determined is called an (e,2e) reaction. Such collisions are known to provide a rich variety of information on collision dynamics and the electronic structure of a target, depending on the kinematics employed. It is now well documented that the momentum-dependent (e,2e) cross-section is directly related to the one-electron momentum density of the ionized orbital, if the measurement is made under the high-energy Bethe ridge conditions where the collision kinematics is described by the electron Compton scattering, analogous to X-ray Compton scattering. Thus building up a more complete knowledge of (e,2e) reaction dynamics at large momentum transfer is vital not only for its fundamental importance but also in providing the unwavering basis for obtaining momentum-density information experimentally. Very recently, we have developed two types of multichannel (e,2e) spectrometers, both of which take advantage of a latest imaging technique. The first spectrometer measures conventional (e,2e) cross-sections, but it features remarkably high sensitivity by simultaneous detection in energy and momentum. The second spectrometer has been developed to examine (e,2e) reactions in the molecular frame, by measuring vector correlations among the two outgoing electrons and the axial-recoil fragment ion. In this contribution details and performance of the two spectrometers will be reported. Our recent studies on (e,2e) reaction dynamics of H2 at large momentum transfer will also be presented, involving the first approach to molecular frame (e,2e) spectroscopy. Emphasis will be placed on the roles played by the firstand second-order terms of the plane-wave Born series model in ionization-excitation processes of H2. Our studies will demonstrate that application of the imaging technique has accelerated rapid advances in (e,2e) spectroscopy.Body: An electron-impact ionizing collision in which the momenta of the incident and two outgoing electrons are determined is called an (e,2e) reaction. Such collisions are known to provide a rich variety of information on collision dynamics and the electronic structure of a target, depending on the kinematics employed. It is now well documented that the momentum-dependent (e,2e) cross-section is directly related to the one-electron momentum density of the ionized orbital, if the measurement is made under the high-energy Bethe ridge conditions where the collision kinematics is described by the electron Compton scattering, analogous to X-ray Compton scattering. Thus building up a more complete knowledge of (e,2e) reaction dynamics at large momentum transfer is vital not only for its fundamental importance but also in providing the unwavering basis for obtaining momentum-density information experimentally. Very recently, we have developed two types of multichannel (e,2e) spectrometers, both of which take advantage of a latest imaging technique. The first spectrometer measures conventional (e,2e) cross-sections, but it features remarkably high sensitivity by simultaneous detection in energy and momentum. The second spectrometer has been developed to examine (e,2e) reactions in the molecular frame, by measuring vector correlations among the two outgoing electrons and the axial-recoil fragment ion. In this contribution details and performance of the two spectrometers will be reported. Our recent studies on (e,2e) reaction dynamics of H2 at large momentum transfer will also be presented, involving the first approach to molecular frame (e,2e) spectroscopy. Emphasis will be placed on the roles played by the firstand second-order terms of the plane-wave Born series model in ionization-excitation processes of H2. Our studies will demonstrate that application of the imaging technique has accelerated rapid advances in (e,2e) spectroscopy. Abstract ID: 62 Photoelectron imaging of negative ions and helium droplets D. Neumark; 1; 1. University of California, Berkeley, Berkeley, CA, USA.ID: 62 Photoelectron imaging of negative ions and helium droplets D. Neumark; 1; 1. University of California, Berkeley, Berkeley, CA, USA. Abstract Body: An overview of several photoelectron imaging experiments in our laboratory will be presented, including time-resolved photoelectron imaging of anion clusters, high resolution slow photoelectron imaging of negative ions and photoelectron imaging of pure and doped helium droplets.Body: An overview of several photoelectron imaging experiments in our laboratory will be presented, including time-resolved photoelectron imaging of anion clusters, high resolution slow photoelectron imaging of negative ions and photoelectron imaging of pure and doped helium droplets. Abstract ID: 63 Velocity map imaging of attosecond and femtosecond dynamics in atoms and small molecules in strong laser fields M. F. Kling; 1; 1. Institute for Atomic and Molecular Physics (AMOLF), FOM, Amsterdam, Netherlands.ID: 63 Velocity map imaging of attosecond and femtosecond dynamics in atoms and small molecules in strong laser fields M. F. Kling; 1; 1. Institute for Atomic and Molecular Physics (AMOLF), FOM, Amsterdam, Netherlands. Abstract Body: In the past decade, the dynamics of atomic and small molecular systems in strong laser fields has received enormous attention,1 but was mainly studied with femtosecond laser fields. First applications of attosecond extreme ultraviolet (XUV) pulse trains (APTs) from high-order harmonic generation (HHG) for the study of atomic and molecular electron and ion dynamics in strong laser fields utilizing the velocity map imaging technique will be highlighted. The APTs were generated in argon from harmonics 13 to 35 of a 35 fs Ti:sapphire laser2 and spatially and temporally overlapped with an intense IR laser field (up to 5x1013 W/cm2) in the interaction region of a velocity map imaging (VMI) machine. The methodology of our approach will be presented for studies on argon. We recorded the velocity distribution of electron wave packets that were strongly driven in the IR laser field after their generation in Ar via single-photon ionization by attosecond XUV pulses. The 3D evolution of the electron wave packets was observed on an attosecond timescale. In addition to earlier experiments with APTs using a magnetic bottle electron time-of-flight spectrometer3 and with single attosecond pulses,4 the angular dependence of the electrons kinetic energies can give further insight into the details of the dynamics. Results that were retrieved for molecular systems, in particular on H2, N2, O2 and CO2 will be highlighted as well. Detailed insight into the attosecond and femtosecond dynamics of these systems in strong laser fields was obtained (e.g., on the alignment, above-threshold ionization, dissociation and coulomb explosion).Body: In the past decade, the dynamics of atomic and small molecular systems in strong laser fields has received enormous attention,1 but was mainly studied with femtosecond laser fields. First applications of attosecond extreme ultraviolet (XUV) pulse trains (APTs) from high-order harmonic generation (HHG) for the study of atomic and molecular electron and ion dynamics in strong laser fields utilizing the velocity map imaging technique will be highlighted. The APTs were generated in argon from harmonics 13 to 35 of a 35 fs Ti:sapphire laser2 and spatially and temporally overlapped with an intense IR laser field (up to 5x1013 W/cm2) in the interaction region of a velocity map imaging (VMI) machine. The methodology of our approach will be presented for studies on argon. We recorded the velocity distribution of electron wave packets that were strongly driven in the IR laser field after their generation in Ar via single-photon ionization by attosecond XUV pulses. The 3D evolution of the electron wave packets was observed on an attosecond timescale. In addition to earlier experiments with APTs using a magnetic bottle electron time-of-flight spectrometer3 and with single attosecond pulses,4 the angular dependence of the electrons kinetic energies can give further insight into the details of the dynamics. Results that were retrieved for molecular systems, in particular on H2, N2, O2 and CO2 will be highlighted as well. Detailed insight into the attosecond and femtosecond dynamics of these systems in strong laser fields was obtained (e.g., on the alignment, above-threshold ionization, dissociation and coulomb explosion). [1] Posthumus, J.H., Rep. Prog. Phys. 2004, 67, 623. [2] López-Martens, R. et al., Phys. Rev. Lett. 2005, 94, 033001. [3] Johnsson, P. et al., Phys. Rev. Lett. 2005, submitted. [4] Goulielmakis, E. et al., Science 2004, 305, 1267. Abstract ID: 64 Momentum imaging with intense laser pulses C. L. Cocke; 1; 1. Physics, Kansas State University, Manhattan, KS, USA.ID: 64 Momentum imaging with intense laser pulses C. L. Cocke; 1; 1. Physics, Kansas State University, Manhattan, KS, USA. Abstract Body: The timing of heavy particle motion in small molecules can be followed in the time domain on a femtosecond scale by using momentum imaging (COLTRIMS) techniques. Several examples will be discussed. First, the kinetic energy release of proton pairs from the double ionization of hydrogen by fast laser pulses is timed using the 2.7 fs optical cycle as a clock. The mechanisms of rescattering, sequential and enhanced ionization are clearly identified in the recoil momentum spectra. Second, pump probe experiments allow us to follow the simultaneous propagation of coherently launched wave packets in different exit channels for H2 and O2. Third, the operation of rescattering double ionization in the case of nitrogen and oxygen molecules will be