Resonant multiphoton ionisation probe of the photodissociation dynamics of ammonia

Abstract

The dissociation dynamics of the Ã-state of ammonia have been studied using a resonant multiphoton ionisation probe in a photoelectron spectroscopy experiment.

Diabatic States at Construction (DAC) through Generalized Singular Value Decomposition

“…Figure a shows the smooth crossing between the diabatic surfaces from GDAC decomposition, and their coupling depicted in Figure b fully splits the two surfaces to produce avoided crossings at geometries in the branching space except for one point, giving rise to a conical intersection in Figure . Similar to the findings in the monomer dissociation, ,, the ground state of the NH 2 product ( 2 B 1 ) correlates diabatically with the excited state of a locally excited NH 3 in the dimer, whereas the excited state of the NH 2 product ( 2 A 1 ) correlates diabatically with the ground state of the dimer complex, which has dominantly ionic character, close to the intersection point. Near the conical interaction, the excited-state surface ( 1 A′) correlates diabatically with interfragment electron transfer in the ionic state of H 2 N – ···NH 4 + , and a proton transfer process occurs on the ground-state surface to yield two ammonia molecules as the (non-productive) photochemical reaction products.…”

Photodissociation dynamics of CH3I probed via multiphoton ionisation photoelectron spectroscopy

“…The decay associated spectra are positive over the full range of energy values, suggesting that the population is decaying into some unmeasured state on an extremely rapid timescale. The enhanced signal over the course of the cross-correlation is due to the enhanced intensity driving a nonresonant multiphoton ionisation processes as seen in our previous experiments using the same methodology, 24 such that the dynamics of the system at this wavelength are defined by the 30 fs decay measured in the second component.…”

“…The majority of the laser and vacuum systems have been described previously [22][23][24] with only small differences to the overall set-up briefly described here. The pump wavelengths, 255 nm and 269 nm, are generated by a high energy OPA (HE-TOPAS) pumped by 8 W of 790 nm light from the amplified output of a femtosecond laser system (KM labs, Red Dragon).…”

“…The CH 3 I molecular beam is created by expanding the room temperature vapour of liquid CH 3 I through a kHz pulsed nozzle (Amsterdam Cantilever 25 ) with a 200 µm aperture. The molecular beam is skimmed before crossing the laser beams at the centre of the velocity map imaging spectrometer interaction region as described in ref 24 . The photoelectron spectrum and angular distributions are obtained from the raw images through polar onion peeling and scaling with the appropriate Jacobian.…”

Ab-initio surface hopping and multiphoton ionisation study of the photodissociation dynamics of CS2

“…The experiment has been described in detail previously [24]. Briefly, an amplified femtosecond laser system (Red Dragon, KM Labs) generates 30 fs pulses of 800 nm light, with a pulse energy of up to 10 mJ at a repetition rate of 1 kHz.…”