Time-resolved photoelectron imaging of complex resonances in molecular nitrogen

Abstract

We have used the FERMI free-electron laser to perform time-resolved photoelectron imaging experiments on a complex group of resonances near 15.38 eV in the absorption spectrum of molecular nitrogen, N2, under jet-cooled conditions. The new data complement and extend the earlier work of Fushitani et al. [Opt. Express 27, 19702–19711 (2019)], who recorded time-resolved photoelectron spectra for this same group of resonances. Time-dependent oscillations are observed in both the photoelectron yields and the photoelectron angular distributions, providing insight into the interactions among the resonant intermediate states. In addition, for most states, we observe an exponential decay of the photoelectron yield that depends on the ionic final state. This observation can be rationalized by the different lifetimes for the intermediate states contributing to a particular ionization channel. Although there are nine resonances within the group, we show that by detecting individual photoelectron final states and their angular dependence, we can identify and differentiate quantum pathways within this complex system.

Trends in angle-resolved molecular photoelectron spectroscopy

“…219 Sub-picosecond time-dependent oscillations in the photoelectron yields and angular distributions, and their decay was assigned to interactions within a complex group of resonances close to the N 2 + (X) ionization threshold at the FERMI FEL. 220 Another example is the determination of the photoemission time delay due to a shape resonance in the N 2 + (X) state using HHG-second harmonic attosecond stereophotoionization interferometry. 221 Photoelectron spectra are one of the most informative probes of quantum states in pump-probe experiments, e.g.…”

Photon energy-resolved velocity map imaging from spectral domain ghost imaging

“…Thanks to their high throughput, 4π collection solid-angle, and ability to provide angle-resolved photoproduct yields, velocity map imaging (VMI) spectrometers [13] have emerged as a popular instrument for time-resolved XFEL studies of dynamics in gas phase systems [3,6,7,[13][14][15][16][17]. A VMI spectrometer typically measures the two-dimensional (2D) projection of the three-dimensional (3D) momentum distribution of charged particles.…”

Spiers Memorial Lecture: prospects for photoelectron spectroscopy

“…Studies of molecular vibrations and bond breaking (in the 10–100 fs range) have been addressed primarily using high power pulsed table-top lasers or FELs, which can attain pulse lengths of a few fs routinely. Time-resolved photoemission has emerged as an important technique in all these ranges, using lab-based high-harmonic generation (HHG) sources, 137 at FELs such as FLASH, 138 the linac coherent light source (LCLS) at Stanford 150 SACLA at SPring-8 151 and FERMI at Elettra, 152 and at synchrotrons including SOLEIL (), ALS 153 and SPring-8. 135…”