Knowledge Bank

The clusters of methane with para-hydrogen molecules $(CH4-(p-H2)nn=1\sim 30)$ were formed in He droplets and studied via laser depletion spectroscopy. The rotationally resolved $\nu 3$ transition of the cluster was observed with changing the number of hydrogen molecules. Large spectral change was seen around $n=12$ and 30, which suggests the completion of the first and second $H2$ solvation shells of the $CH4$ molecule. The aggregate state of the $H2$ cluster is discussed.