molecular spectroscopy 

https://doi.org/10.1351/goldbook.08217
Measurement principle of spectroscopy for the study of rotational, vibrational, and electronic transitions of molecules.
Note:
Molecular spectra may be emission or absorption spectra.
Source:
PAC, 2021, 93, 647. (Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)) on page 649 [Terms] [Paper]