Photoelectron imaging and photodissociation of ozonide in O3− ⋅ (O2)n (n = 1-4) clusters

Abstract

The photoelectron images of O3 (-) and O3 (-) ⋅ (O2)n (n = 1-4) have been measured using 3.49 eV photon energy. The spectra exhibit several processes, including direct photodetachment and photodissociation with photodetachment of O(-) photofragments. Several spectra also exhibit autodetachment of vibrationally excited O2 (-) photofragments. Comparison of the bare O3 (-) photoelectron spectra to that of the complexes shows that the O3 (-) core is preserved upon clustering with several O2 molecules, though subtle changes in the Franck-Condon profile of the ground state photodetachment transition suggest some charge transfer from O3 (-) to the O2 molecules. The electron affinities of the complexes increase by less than 0.1 eV with each additional O2 molecule, which is comparable to the corresponding binding energy [K. Hiraoka, Chem. Phys. 125, 439-444 (1988)]. The relative intensity of the photofragment O(-) detachment signal to the O3 (-) ⋅ (O2)n direct detachment signal increases with cluster size. O2 (-) autodetachment signal is only observed in the O3 (-), O3 (-) ⋅ (O2)3, and O3 (-) ⋅ (O2)4 spectra, suggesting that the energy of the dissociative state also varies with the number of O2 molecules present in the cluster.

Photoelectron-Photofragment Coincidence Spectroscopy With Ions Prepared in a Cryogenic Octopole Accumulation Trap: Collisional Excitation and Buffer Gas Cooling

“…The effects of varying buffer gas conditions can be seen in the total photoelectron spectra (electrons in coincidence with both dissociative products and stable O 3 ) in Figure 5. The peaks at low eKE (0.07, 0.19, and 0.32 eV) originate from the photodissociation/autodetachment O3- + hν → O2-( 2 Π) + O( 3 P) pathway (2) via photoexcitation to the 2 A 2 excited state as previously reported (Mann et al, 2015; Shen et al, 2017). At E hν = 3.20 eV, access to O2-(v″ = 4,5,6) is energetically forbidden without vibrational excitation of O3-, as shown in the energetics diagram in Figure 1, so observation of vibrationally auto detaching O2- provides a sensitive test of parent anion internal energy.…”

“…The capabilities of COAT are demonstrated here by comparing the signatures of the three concurrent photophysical channels occurring at E hν = 3.20 eV in the photoelectron spectra of O3-: (1) photodetachment O3- + hν → O 3 + e − , (2) photodissociation/autodetachment O3- + hν → O2-(2Πg) + O( 3 P), and (3) photodissociation O3- + hν → O − ( 2 P) + O 2 (1Δg) followed by the photodetachment O − ( 2 P) + hν → O( 3 P) by a second photon. The primary spectroscopic feature of channel (1) is a structured photoelectron spectrum in the 0.30–1.50 eV eKE range (Novick et al, 1979; Arnold et al, 1994; Garner et al, 1997; Mann et al, 2015). Channel (2) is observed in the spectra as a structured signal at low eKE (0.0–0.4 eV) originating from sequential autodetachment of O2-(v″ > 4).…”

Identification of Isoprene Oxidation Reaction Products via Anion Photoelectron Spectroscopy

“…Experimental. Anionic species resulting from the oxidation of isoprene under several different conditions were massanalyzed and spectroscopically probed via anion PE spectroscopy using an anion PE imaging apparatus that has been described previously, 50 and thus only a brief description follows. As noted above, isoprene-based species were generated under several different oxidizing conditions, with ionization achieved by passing the species through a pulsed discharge source described below.…”

Autodetachment over Broad Photon Energy Ranges in the Anion Photoelectron Spectra of [O2–M]− (M = Glyoxal, Methylglyoxal, or Biacetyl) Complex Anions

“…The lowest-lying excited neutral state would be the overall singlet O 2 ( 1 Δ g ) + trans-glyoxal (S 0 ). 56 The anion PE spectra of previously studied O 2 − •VOC IMCs primarily exhibited a direct detachment signal having spectral Franck−Condon profiles like that of bare O 2 − but broadened and shifted to higher electron binding energy. This effect is due to the stabilization of O 2 − by the partner, in addition to Franck− Condon overlap between the IMC and the dissociative portion of the neutral O 2 − VOC potential.…”