A method for analyzing a plurality of molecules with cryogenic vibrational spectroscopy including the steps of providing a packet of molecules in a ionized form, injecting the packet into an ion mobility section, spatially separating the ions of the packet into subpackets according to their collisional cross section (CCS), recompressing the subpackets, by removing an empty space between them, loading the ions into a cryogenic ion trap by keeping subpackets with different collisional cross section in a respective separate compartment, cooling the ions in collisions with a buffer gas, tagging the ions by attaching a messenger molecule, sending a pulse to the trap to excite vibrations of the cold, trapped, and messenger-tagged ions, and separately ejecting ion subpacket from the trap into an extraction region of a time-of-flight mass spectrometer and measuring the number of remaining messenger-tagged ions and untagged ions for each subpacket.