Conical-intersection dynamics and ground-state chemistry probed by extreme-ultraviolet time-resolved photoelectron spectroscopy

Abstract

Time-resolved photoelectron spectroscopy (TRPES) is a useful approach to elucidate the coupled electronic-nuclear quantum dynamics underlying chemical processes, but has remained limited by the use of low photon energies. Here, we demonstrate the general advantages of XUV-TRPES through an application to NO2, one of the simplest species displaying the complexity of a non-adiabatic photochemical process. The high photon energy enables ionization from the entire geometrical configuration space, giving access to the true dynamics of the system. Specifically, the technique reveals dynamics through a conical intersection, large-amplitude motion and photodissociation in the electronic ground state. XUV-TRPES simultaneously projects the excited-state wave packet onto many final states, offering a multi-dimensional view of the coupled electronic and nuclear dynamics. Our interpretations are supported by ab initio wavepacket calculations on new global potential-energy surfaces. The presented results contribute to establish XUV-TRPES as a powerful technique providing a complete picture of ultrafast chemical dynamics from photoexcitation to the final products.

Direct mapping of curve-crossing dynamics in IBr by attosecond transient absorption spectroscopy

“…Experimentally, few-femtosecond time resolution is required for the probe, and the intrinsic degeneracy makes it challenging to obtain state-resolved information. Several experimental methods have been applied to this end (11)(12)(13)(14)(15), including high-harmonic spectroscopy (16) and ultrafast electron diffraction (17). Recent theoretical studies predicted that transient absorption spectroscopy in the x-ray/extremeultraviolet (XUV) range offers a distinct and powerful route to measure excited-state dynamics around nonadiabatic regions, with core-level absorption capturing the marked reorganization of valence electrons (18,19).…”

Ab initio calculation of femtosecond-time-resolved photoelectron spectra of NO2 after excitation to the A-band

“…In this article, we concentrate on the analysis of the time-dependent photoelectron spectra generated by these short pulses. The comparison of calculations with longer pulses and experimental data will be shown in a future publication 24 . We consider all transitions from the neutral (1) 2 A and (2) 2 A states to each of the energetically lowest-lying two states of x 0.5 with the transition matrix elements set to 1, as illustrated in panel c, shows the strong modulations due to the movement of the wave packet.…”

“…Recently, some of the present authors have applied extreme-ultraviolet (XUV)-TRPES to the same excited-state dynamics in NO 2 24 . The application of single-photon ionization removes the complications induced by the high peak intensities and reveals the genuine dynamics of the photo-excited molecular system over its complete reaction path.…”

“…We present the results of full-dimensional quantum-mechanical wave-packet calculations on these novel surfaces. Subsequently, we report the calculation of time-dependent photoelectron spectra for comparison with recent experimental data from XUV-TRPES 24 in an extended range of binding energies for the channels leading to the two lowest lying states of 1 A , 1 A ,…”

NaI revisited: Theoretical investigation of predissociation via ultrafast XUV transient absorption spectroscopy

“…[16][17][18][19][20] Those elusive processes have been a subject of numerous spectroscopic studies for their ubiquitous role in steering the outcome of photochemical reactions. 15,[21][22][23][24][25][26][27][28][29][30][31][32][33][34] Despite the established concept of potential crossings, their experimental observation is still considered challenging, as it requires few-femtosecond time resolution and a capability to resolve closely-spaced electronic states by the probe method.…”