The baseline offset in the FTIR spectra is due to the background being air and the sample being inside a 'Linkam cell' with transmission losses through the heater block and reflection losses from four CaF2 windows

SP = 'temperature setpoint of the heater block' act = actual temperature +/- ~10 C (estimated as described in J.Chem. Phys. 158, 114201 (2023))

Samples prepared and 2D-IR data acquired as described in "Distinctive signatures and ultrafast dynamics of Bronsted sites, silanol nests and adsorbed water in zeolites revealed by 2D-IR spectroscopy", 
Donaldson et al, Chemical Science 2025

2D-IR spectra are tab separated

The pump axis is row 1
The probe axis of parallel and perpendicular detectors respectively are column 1