We performed a study of the single ionization of iodine, I 2 over a range of wavelengths. Single ionization of I 2 is unexpectedly found to have a contribution from inner molecular orbitals involving the 5s electrons. The I + I + dissociation channel was recorded through velocity map imaging and the kinetic energy release of each channel was determined with 2D fitting of the images. Most of the measured kinetic energy data were inconsistent with ionization to the X, A, and B states of I + 2 , implying ionization from deeper orbitals. A pump-probe Fourier transform technique was used to look for modulation at the X and A state vibrational frequencies, to see if they were intermediate states in a two step process. X and A state modulation was only seen for kinetic energy releases below 0.2 eV consistent with dissociation through the B state. From these results and intensity, polarization, and wavelength dependent experiments we found no evidence of bond softening, electron rescattering or photon mediation through the X or A states to higher energy single ionization channels.

Optical pumping of molecules provides unique opportunities for control of chemical reactions at a wide range of rotational energies. This work reports a chemical reaction with extreme rotational excitation of a reactant and its kinetic characterization. We investigate the chemical reactivity for the hydrogen abstraction reaction SiO+ + H2 → SiOH+ + H in an ion trap. The SiO+ cations are prepared in a narrow rotational state distribution, including super-rotor states with rotational quantum number (j) as high as 170, using a broad-band optical pumping method. We show that the super-rotor states of SiO+ substantially enhance the reaction rate, a trend reproduced by complementary theoretical studies. We reveal the mechanism for the rotational enhancement of the reactivity to be a strong coupling of the SiO+ rotational mode with the reaction coordinate at the transition state on the dominant dynamical pathway.

Optical pumping of molecules provides unique opportunities for control of chemical reactions at a wide range of rotational energies. Chemical reactivity for the hydrogen abstraction reaction SiO + + H2 → SiOH + + H is investigated in an ion trap. The SiO + cation is prepared with a narrow rotational state distribution, including super-rotor states with rotational quantum number (j ) as high as 170 using a broad-band optical pumping method. The super-rotor states of SiO + are shown to substantially enhance the reaction rate, a trend reproduced by complementary theoretical studies. The mechanism for the rotational enhancement of the reactivity is revealed to be a strong coupling of the SiO + rotational mode with the reaction coordinate at the transition state on the dominant dynamical pathway. This work reports for the first time a chemical reaction with extreme rotational excitation of a reactant and its kinetic characterization.

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