Baseline correction methods to deal with artifacts in femtosecond transient absorption spectroscopy.

In femtosecond transient absorption spectroscopy, artifact contributions are usually observed at ultra-short time scale. These complex signals are very challenging because of their nature, related to ultrafast phenomena, and because they strongly distort the structure of the spectrokinetic data. The purpose of this work is to evaluate the potential of baseline correction methods for femtosecond transient absorption spectroscopy data pre-processing. Indeed, artifacts removal should ideally be performed before multivariate data analysis. The work is thus mainly focused on two different approaches which are filtering by discrete wavelet transform, on the one hand, and smoothing by asymmetric least squares, on the other hand. The results obtained both on simulated data and on femtosecond pump-probe spectroscopy data are discussed. It can be concluded that asymmetric least squares smoothing procedure turns out to perform satisfactory for artifacts removal. Indeed, only mild discrepancies are observed in the transient spectra and, most important, good recovery of the kinetics is obtained at ultra-short time scale.