Abstract
Attosecond transient absorption spectroscopy (ATAS) is used to observe photoexcited dynamics with outstanding time resolution. The main experimental challenge of this technique is that high-harmonic generation sources show significant instabilities, resulting in sub-par sensitivity when compared to other techniques. This paper proposes edge-pixel referencing as a means to suppress this noise. Two approaches are introduced: the first is deterministic and uses a correlation analysis, while the second relies on singular value decomposition. Each method is demonstrated and quantified on a noisy measurement taken on WS2 and results in a fivefold increase in sensitivity. The combination of the two methods ensures the fidelity of the procedure and can be implemented on live data collection but also on existing datasets. The results show that edge-referencing methods bring the sensitivity of ATAS near the detector noise floor. An implementation of the post-processing code is provided to the reader.
Highlights
Transient absorption experiments are frequently performed in the extreme ultraviolet (XUV) and X-ray regimes, taking advantage of the element specificity and the sensitivity to local structural and electronic environments offered by these radiations
The crudest measurement procedure used in the early days of Attosecond transient absorption spectroscopy (ATAS) consisted of measuring the time-dependent transmitted spectrum I1 with the pump on at each time delay, and to divide each time step by the probe spectrum measured at a negative time delay ()
We have presented two general noise suppression schemes for ATAS that can be implemented either during data collection or applied at the post-treament stage
Summary
Transient absorption experiments are frequently performed in the extreme ultraviolet (XUV) and X-ray regimes, taking advantage of the element specificity and the sensitivity to local structural and electronic environments offered by these radiations The earliest of these experiments emerged more than 30 years ago [1, 2] and used laser-produced plasmas as X-ray sources. Experiments are commonly performed on gas, liquid and solid targets, for instance at large instrument facilities such as synchrotrons [3, 4] and free-electron lasers [5] While these sources offer freely tunable and high flux Xray radiation, they suffer from a probe bandwidth which is intrinsically narrow (¡ 1 eV) compared to absorption edges. This allows to perform attosecond transient absorption spectroscopy (ATAS), in which multiple absorption edges are covered in one laser shot and where time resolutions are on the order of attoseconds [6, 7]
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