  We discuss layout and performance of a high-resolution Stimulated Raman Loss
spectrometer that has been newly developed for accurate studies of spectral
lineshapes and line center frequencies of hydrogen isotopologues and in general
of Raman active transitions. Thanks to the frequency comb calibration of the
detuning between pump and Stokes lasers and to an active alignment of the two
beams, the frequency accuracy is well below 100 kHz. Over the vertical axis the
spectrometer benefits from shot-noise limited detection, signal enhancement via
multipass cell, active flattening of the spectral baseline and measurement
times of few seconds over spectral spans larger than 10 GHz. Under these
conditions an efficient averaging of Raman spectra is possible over long
measurement times with minimal distortion of spectral lineshapes. By changing
the pump laser, transitions can be covered in a very broad frequency span, from
50 to 5000 $\mathrm{cm^{-1}}$, including both vibrational and rotational bands.
The spectrometer has been developed for studies of fundamental and collisional
physics of hydrogen isotopologues and has been recently applied to the
metrology of the Q(1) 1-0 line of $\mathrm{H_2}$.
