Analytic modeling of structures in attosecond transient-absorption spectra

Abstract

Attosecond transient-absorption spectroscopy (ATAS) is an established method for exploring electron dynamics on the subfemtosecond time scale. ATAS spectra contain certain ubiquitous features, such as oscillating fringes, light-induced structures, and hyperbolic sidebands, representing physical processes. We derive closed analytical expressions describing these features, based on a three-level system responding adiabatically to the influence of an infrared field in conjunction with an extreme ultraviolet pulse, and use He to illustrate the theory. The validity of the formulas is substantiated by comparing their predictions with spectra calculated numerically by the time-dependent Schrödinger equation. The closed analytical forms and the details of their derivation resolve the origins of the features.

Attosecond transient-absorption spectroscopy of polar molecules

“…In experimental settings, finite detector resolution and collisional broadening are effects that can lead to dephasing of the time-dependent dipole moment. A common approach [6,14,39] is to impose a window function W (t − τ 0 ) in order to mimic this behavior in simulations. The function, which brings D tot (t) to zero over a given time interval, is defined as…”

“…The most common features have been studied extensively, and include light-induced structures (LISs) indicating the presence of virtual intermediate states involved in multi-photon processes [26,27]; oscillating fringes arising from the dressing of populated * lun yue@msn.com states by the NIR-pulse [28,29]; hyperbolic sidebands adjacent to absorption lines, associated with perturbed free-induction decay [30,31]; and modification of absorption lines [32][33][34][35], typically by Stark shifts [36], such as Autler-Townes splitting [37,38]. Our previous work [39] supplemented the existing studies with analytical expressions describing several of these features.…”

Light-induced states in the transient-absorption spectrum of a periodically pumped strong-field-excited system

“…An explicit solution of Eq. (19) in this single-pulse case allows one to introduce the probe-and pump-pulse interaction operatorŝ…”

Nonadiabatic effects in attosecond transient absorption spectroscopy

“…In atoms, ATAS has been used to observe the motion of valence electrons in Kr [4], autoionization in Ar [5], AC Stark shift in Kr [6] and He [7], electron wave packets in He [8,9] and dynamics in Xe [10,11]. Typical features of ATA spectra [12] include Autler-Towes splitting of absorption lines [13,14], oscillating fringes around bright states coming from three-photon interference [15,16], light-induced structures (LIS) around dark states attributed to two-photon interference [17] and hyperbolic sidebands around the main absorption lines associated with free-induction decay (see, e.g., the discussion in Ref. [12]).…”

“…Typical features of ATA spectra [12] include Autler-Towes splitting of absorption lines [13,14], oscillating fringes around bright states coming from three-photon interference [15,16], light-induced structures (LIS) around dark states attributed to two-photon interference [17] and hyperbolic sidebands around the main absorption lines associated with free-induction decay (see, e.g., the discussion in Ref. [12]).…”