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Methyl vinyl ketone (C4H6O) is a volatile, labile organic compound of importance in atmospheric chemistry. We prepared a molecular beam of methyl vinyl ketone with a rotational temperature of 1.2(2) K and demonstrated the spatial separation of the s-cisand s-transconformers of methyl vinyl ketone using the electrostatic deflector. The resulting sample density was 1.5(2) × 108cm–3for the direct beam in the laser ionization region. These conformer-selected methyl vinyl ketone samples are well suited for conformer-specific chemical reactivity studies such as in Diels–Alder cycloaddition reactions.

Spatial separation of water dimers from water monomers and larger water clusters through the electric deflector is presented. A beam of water dimers with 93% purity and a rotational temperature of 1.5 K was obtained. Following strong-field ionization using a 35 fs laser pulse with a wavelength centered around 800 nm and a peak intensity of 1014W/cm2, we observed proton transfer and 46% of ionized water dimers broke apart into hydronium ions H3O+and neutral OH.

Strong field double ionization that triggers the chemical bond rearrangement of CH3Cl is investigated by impulsive control of the alignment of molecules. The alignment and laser intensity dependent H2+and H3+yields in linearly polarized femtosecond laser have been measured, and the obtained data show that the maximum signal of H2+appears at the laser polarization parallel to the C–Cl axis of molecules and H3+species are more likely to eject at the laser polarization parallel to the C–Cl axis at low laser intensity while the H3+signal peaks at laser polarization perpendicular to the C–Cl axis at high laser intensity. The measurements indicate that electrons from HOMO – 1 and HOMO – 2 orbitals have been ionized for the generation of bond rearrangement at different laser intensity. Our results demonstrate the importance of multielectron effects and also provide an effective control method in the process of chemical bond rearrangement of the molecules in strong laser fields.