HCN CLUSTERS IN MOLECULAR-BEAMS AND CRYOGENIC MATRICES

Cluster formation of hydrogen cyanide (HCN) was traced by mass spectro scopy in molecular beams and by FTIR spectroscopy in cryogenic matrice s in which the clusters were embedded. Both experiments provided evide nce for the presence of linear (n greater than or equal to 2) and cycl ic structures (n greater than or equal to 3) which were predicted by a b initio calculations as comparably stable. The mass spectra clearly r eflect a fundamentally different behaviour of the two types of cluster s within the expansion zone: the linear species exhibit the cabability of cluster growth, while the cyclic ones do not. This leads to a char acteristic size distribution with two marked maxima. During matrix dep osition, considerable distortions of the clusters are created which ma y be healed out by annealing. The resulting sharp bands in the CH stre tching region were assigned in agreement with ab initio calculations a nd previous IR studies aiming at small linear and cyclic species (n le ss than or equal to 3) in diverse liquid and solid environments.