Resonance‐Mediated Below‐Threshold Delayed Photoemission and Non‐Franck–Condon Photodissociation of Cold Oxyallyl Anions

Simultaneous electrostatic trapping of merged cation & anion beams

Simultaneous trapping of merged cation and anion beams in the hybrid electrostatic ion beam trap (HEIBT) opens new opportunities for the study of the interactions of isolated atomic molecular or cluster ions with oppositely charged ionic species. Application of the trapped merged beams requires a detailed understanding of the trapping dynamics and the effect of the Coulombic attractive and repulsive forces between the ions on their motion in the trap. The simultaneous trapping regime is explored experimentally for SF6- anion and SF5+ cation beams and compared to realistic ion trajectory simulations. The respective stability of the simultaneously trapped cation and anion beams is experimentally tracked by nondestructive and mass sensitive image charge monitoring. An approximate analytical potential model is presented for modeling the dynamics of trapped ions, providing insight into the role of ion-ion interactions, and suggesting a simplified mirror design.

Nonadiabatic Dynamics between Valence, Nonvalence, and Continuum Electronic States in a Heteropolycyclic Aromatic Hydrocarbon

Internal conversion between valence-localized and dipole-bound states is thought to be a ubiquitous process in polar molecular anions, yet there is limited direct evidence. Here, photodetachment action spectroscopy and time-resolved photoelectron imaging with a heteropolycyclic aromatic hydrocarbon (hetero-PAH) anion, deprotonated 1-pyrenol, is used to demonstrate a subpicosecond (τ₁ = 160 ± 20 fs) valence to dipole-bound state internal conversion following excitation of the origin transition of the first valence-localized excited state. The internal conversion dynamics are evident in the photoelectron spectra and in the photoelectron angular distributions (β₂ values) as the electronic character of the excited state population changes from valence to nonvalence. The dipole-bound state subsequently decays through mode-specific vibrational autodetachment with a lifetime τ₂ = 11 ± 2 ps. These internal conversion and autodetachment dynamics are likely common in molecular anions but difficult to fingerprint due to the transient existence of the dipole-bound state. Potential implications of the present excited state dynamics for interstellar hetero-PAH anion formation are discussed.

Hybrid electrostatic ion beam trap (HEIBT): Design and simulation of ion-ion, ion-neutral, and ion-laser interactions

Using dichroic electrostatic mirrors, which can reflect a fast ion beam while transmitting a counterion beam, allows extending the field of electrostatic ion trapping. We present the design and simulations of a hybrid electrostatic ion beam trap that allows simultaneous trapping of velocity matched cation and anion beams. The possible merged beam ion-ion, ion-neutral, and ion-laser experiments are discussed.