Time-resolved quantum beats in the fluorescence of helium resonantly excited by XUV radiation

Abstract

We report on the observation of time-resolved quantum beats in the helium fluorescence from the transition 1s3p → 1s2s, where the initial state is excited by XUV free electron laser radiation. The quantum beats originate from the Zeeman splitting of the magnetic substates due to an external magnetic field. We perform a systematic study of this effect and discuss the possibilities of studying this phenomenon in the XUV and X-ray regime.

Ultra-short-pulse high-average-power megahertz-repetition-rate coherent extreme-ultraviolet light source

“…This record XUV power together with the cutoff enhancement is enabled by a new-class of driving laser providing a unique combination of a short wavelength (515 nm) and a short pulse duration (18.6 fs) at a record high average power of 51 W. Compared to state-of-the art XUV sources, the provided average power is one order of magnitude higher and the pulse duration is significantly shorter, which represents a major milestone for upcoming applications of coherent XUV radiation in science and technology. This will greatly advance and facilitate XUV application in various fields e.g investigating fastest dynamics using photoelectron emission spectroscopy, coincidence measurements, XUV-ionization and absorption spectroscopy, fluorescence spectroscopy, ultrafast XUV imaging and XUV-pump XUV-probe experiments, among others [10][11][12][13][14][15][16][17]19,20 . Due to the excellent scaling possibilities of energetic ultrafast Yb-based fibre lasers and the components for pulse compression to the kW-level and beyond 24,34,35 , even upscaling of the presented approach to the 100 mW level seems possible.…”

“…1). An increase in XUV average power would help for example to mitigate space charge effects in photoelectron emission spectroscopy [17] (at high repetition rates), as well as to shorten acquisition times and, hence, enhance the signal-to-noise ratio in (time-resolved) coincidence measurements [18], XUVabsorption spectroscopy [19], XUV-ionization spectroscopy [20], coherent diffractive imaging of ultrafast magnetization dynamics [21], fluorescence spectroscopy [22] and XUV-pump XUV-probe experiments [23,24], among others. Furthermore, shortest pulses are desired to investigate fastest dynamics in atoms [6,25], molecules [26], ions [23], solids [19] and compound materials [27].…”

Multipass cell post-compression at 515 nm as an efficient driver for a table-top 13.5 nm source

“…High harmonic generation (HHG) allows for the creation of coherent radiation in the extreme ultraviolet (XUV/EUV) spectral region. The access to this spectral region, through the means of a lab-scale setup, enabled a plethora of applications such as the investigation of electron dynamics in matter [2], spectroscopic analysis [3] and coherent diffractive imaging (CDI) [4]. Where in recent years the spectral region at 92 eV has gained particular interest due to its use in EUV-lithography [5].…”