Optical afterglow spectra of GRB 180325A (in the extinction bump region) at four epochs observed with the NOT/AlFOSC and VLT/X-shooter instruments. Each color corresponds to a different epoch and mid-times of observations are indicated in the corresponding color. Inset: shown is the VLT/X-shooter spectrum and corresponding noise spectrum (blue dotted line) in the Lyα absorption-line region. The red solid and dashed lines show the best-fit H I column density profile and 1σ error, respectively.