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

Abstract

Laser initiated reactions in N2O clusters studied by time-sliced ion velocity imaging technique J. Chem. Phys. 139, 044307 (2013) 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 N 2 photoproducts from N 2 O or from molecular beam cooled N 2 . 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 N 2 O. 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, v 2 , 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, v 2 ≤ 7, 0). These results agree well with previous work at lower values of v 2 , both experimental and theoretical. The dissociation energy of N 2 O with respect to the O( 1 D) + N 2 1 + g asymptote was determined to be 3.65 ± 0.02 eV.

Photodissociation Dynamics of Nitrous Oxide near 145 nm: The O(1S0) and O(3PJ=2,1,0) Product Channels

“…(4) Because of detection efficiency for O atom with different electronic states and spin−orbit states, the branching ratios of different dissociation channels are hard to be determined. (5) The results acquired at wavelengths near the valleys display slightly higher vibrational excitation than that obtained at wavelengths near the peaks (please see the Supporting Information). Therefore, we can deduce that, for the O( 1 S 0 ) + N 2 (X 1 Σ g + ) dissociation channel near 145 nm, nonadiabatic coupling between the C( 1 Π) and the D 1 Σ + state plays an important role.…”

Rotationally Resolved Vacuum Ultraviolet Resonance-Enhanced Multiphoton Ionization (VUV REMPI) of Acetylene via the G̃ Rydberg State

“…The experiments are performed using a molecular beam apparatus which has been described in detail previously. 18 Here, for most of the measurements, we use a time-of-flight configuration with Wiley−McLaren extraction fields 19 and read the ion signal from the back of the MCP instead of using the slice imaging configuration and position sensitive detection. The heated pulsed nozzle 18,20 was used to increase the population of vibrationally excited states, helping to identify hot bands.…”

“…18 Here, for most of the measurements, we use a time-of-flight configuration with Wiley−McLaren extraction fields 19 and read the ion signal from the back of the MCP instead of using the slice imaging configuration and position sensitive detection. The heated pulsed nozzle 18,20 was used to increase the population of vibrationally excited states, helping to identify hot bands. In contrast to an effusive beam or a gas cell where the sample will have a Boltzmann population, the beam produced in this way still undergoes significant rotational cooling, leading to different effective temperatures for rotation and vibration.…”

Full-dimensional quantum molecular dynamics calculations of the rovibrationally mediated X 1A′ → 2 1A′′ transition of nitrous oxide

“…Photodissociation of atmospheric nitrous oxide (N 2 O) is a topic of great interest and has received considerable experimental and theoretical attention in recent years . N 2 O is a prominent greenhouse gas that plays an important role in ozone depletion.…”