Single-field slice-imaging with a movable repeller: Photodissociation of N2O from a hot nozzle.

We present a new photo-fragment imaging spectrometer, which employs a movable repeller in a single field imaging geometry. This innovation offers two principal advantages. First, the optimal fields for velocity mapping can easily be achieved even using a large molecular beam diameter (5 mm); the velocity resolution (better than 1%) is sufficient to easily resolve photo-electron recoil in (2 + 1) resonant enhanced multiphoton ionization of N₂ photoproducts from N₂O or from molecular beam cooled N₂. Second, rapid changes between spatial imaging, velocity mapping, and slice imaging are straightforward. We demonstrate this technique's utility in a re-investigation of the photodissociation of N₂O. Using a hot nozzle, we observe slice images that strongly depend on nozzle temperature. Our data indicate that in our hot nozzle expansion, only pure bending vibrations - (0, v₂,0) - are populated, as vibrational excitation in pure stretching or bend-stretch combination modes are quenched via collisional near-resonant V-V energy transfer to the nearly degenerate bending states. We derive vibrationally state resolved absolute absorption cross-sections for (0, v₂ < 7, 0). These results agree well with previous work at lower values of v₂, both experimental and theoretical. The dissociation energy of N₂O with respect to the O(¹D) + N₂¹Σ_g⁺ asymptote was determined to be 3.65 ± 0.02 eV. [ABSTRACT FROM AUTHOR]