Symmetry of molecular Rydberg states revealed by XUV transient absorption spectroscopy

Abstract

Transient absorption spectroscopy is utilized extensively for measurements of bound- and quasibound-state dynamics of atoms and molecules. The extension of this technique into the extreme ultraviolet (XUV) region with attosecond pulses has the potential to attain unprecedented time resolution. Here we apply this technique to aligned-in-space molecules. The XUV pulses are much shorter than the time during which the molecules remain aligned, typically 100 fs. However, transient absorption is not an instantaneous probe, because long-lived coherences re-emit for picoseconds to nanoseconds. Due to dephasing of the rotational wavepacket, it is not clear if these coherences will be evident in the absorption spectrum, and whether the properties of the initial excitations will be preserved. We studied Rydberg states of N and O from 12 to 23 eV. We were able to determine the polarization direction of the electronic transitions, and hence identify the symmetry of the final states.

Laser Driven Fluorescence Emission in a Nitrogen Gas Jet at 100 MHz Repetition Rate

“…Under such circumstances, it is reasonable to eliminate the ISC mechanism and the dissociative recombination mechanism as the predominant candidates. For these mechanisms, at least one step takes much longer than a few picoseconds [46,52,53]. Besides, as also demonstrated in our experiment with polarization dependence and flow rate dependence measurements, these mechanisms are in contradiction to our observations as well.…”

Coupled nuclear–electronic decay dynamics of O2 inner valence excited states revealed by attosecond XUV wave-mixing spectroscopy

“…The Rydberg series converging to the O2 + Σ − 4 state represent a good model to study such competing decay dynamics and have thus been extensively investigated during the past few decades. [8][9][10][11][12][13][14][15][16][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] The interaction of O2 with 20-25 eV extreme ultraviolet (XUV) photons excites an inner shell 2σu electron to the Rydberg states comprising these series. There are two such series observed in the XUV absorption spectrum, denoted as 2 −1 ( = 0,2), here abbreviated as ns and nd Rydberg series.…”

Photo-ionization Initiated Differential Ultrafast Charge Migration: Impact of Molecular Symmetries and Tautomeric Forms

“…ATAS, on the other side, relies on high density samples for achieving a good signal to noise ration. We will, therefore, probably need to make a compromise between the degree of alignment and the molecular beam density, such that we still get a good alignment, and thus selectivity, and perform ATAS [69]. This can be solved by performing the COLTRIMS measurement first with a lower density gas jet, then after switching off the sensitive electronics one can increase the pressure which makes absorption of the XUV measureable.…”