Ultrafast molecular dynamics are frequently extracted
from two-dimensional
(2D) spectra via the center line slope (CLS) method. The CLS method
depends on the accurate determination of frequencies where the 2D
signal is at a maximum, and multiple approaches exist for the determination
of that maximum. Various versions of peak fitting for CLS analyses
have been utilized; however, the impact of peak fitting on the accuracy
and precision of the CLS method has not been reported in detail. Here,
we evaluate several versions of CLS analyses using both simulated
and experimental 2D spectra. The CLS method was found to be significantly
more robust when fits were used to extract the maxima, particularly
fitting methods that utilize pairs of opposite-sign peaks. However,
we also observed that pairs of opposite-signed peaks required more
assumptions than single peaks, which are important to check when interpreting
experimental spectra using peak pairs.