Photoelectron spectroscopy of ammonia via a fast predissociative state

Abstract

We report a study on resonance enhanced multiphoton ionization photoelectron spectroscopy (REMPI-PES) involving the fast predissociative state of ammonia, using A 3 nano-and femtosecond lasers. The multiphoton scheme involves (1 ] 1), (2 ] 2), (2 ] 2) ] 1 and (2 ] 2) ] 2 photon processes. We have found a progression of stretching vibrations in the PE spectrum when pumping 1 and 3 as intermediateThe stretching vibration intensity distributions in the photoelectron spectrum are calculated by using the Chebychev method of the wavepacket propagation. The femtosecond spectrum shows a similar feature to the nanosecond spectrum. However, high laser power also causes band broadening and shifting e †ect as well as above threshold multiphoton ionization.

Observation of ultrafast NH3 (Ã) state relaxation dynamics using a combination of time-resolved photoelectron spectroscopy and photoproduct detection

“…This assignment suggests that the dominant ionization mechanism follows a Dn 2 , Dn 1 = 0 propensity rule. This is in-line with earlier findings from fs REMPI-PES experiments on ionization from the NH 3 (A ˜) state, 14 but differs from the observation of a Dn 1 = 1 rule observed after excitation to, and ionization from, the higher lying NH 3 (E ˜) state. 30 Photoelectron peaks ii and iv are assigned to the umbrella progression in the cation, where only even 2 m quanta are present for ionization from n 0 2 ¼ 2 and 4 levels, and only odd 2 m quanta are present for ionization from n 0 2 ¼ 3 and 5 levels.…”

“…Plots are presented in this manner to afford assignment of photoelectron peaks to known vibronic levels in the cationic ground state, NH 3 + (X ˜) . 14,[38][39][40] Four peaks are seen in each of the n 0 2 ¼ 2 À 5 spectra-referred to as peaks i, ii, iii, and iv, from left to right within each panel of Fig. 3 (see panel (b)).…”

“…[7][8][9] The NH 3 (A ˜) absorption bands show no rotational fine structure and analysis of vibrational lineshapes has shown that dissociation of the n 0 2 ¼ 0 À 6 levels occurs within 100 femtoseconds (fs). 7,10 A detailed model of NH 3 (A ˜) dissociation has followed from various experimental techniques including laser induced fluorescence (LIF), [11][12][13] resonance enhanced multi-photon ionization photoelectron spectroscopy (REMPI-PES), 14 and H-atom photofragment translation spectroscopy (PTS). [15][16][17][18][19] The NH 3 (A ˜) and NH 3 (X ˜) potential energy surfaces have been calculated as a function of the out-of-plane bending angle, y, and the H 2 N-H bond distance, R N-H .…”

Resonant multiphoton ionisation probe of the photodissociation dynamics of ammonia

“…where ω ei and ω ei χ ei are the harmonic and anharmonic vibrational frequencies of the ith vibrational mode of the ground ion state of ammonia and v i is the vibrational quantum number of the state populated. The literature values used are taken from Xie et al [30] and result in the expected kinetic energies given in table I and assignments shown in figure 1 as the combs above the data. The assignments highlight a progression in the symmetric stretch, ν 1 , in combination with various quanta in the umbrella mode, ν 2 .…”

A Novel Ionization Path of Nitric Oxide: Resonance, Not Perturbation, Plays a Role

“…The response of coupled electron ± nuclear motion under an ultrastrong laser field has also been studied by adopting the same technique. [8,9] Nitric oxide, as a prototype, has been extensively studied using multiphoton ionization because of its low ionization potential. [10±12] Usually, the A 2 S and C 2 P states of nitric oxide are used as the intermediate resonance levels.…”