Spectroscopic studies of nickel and iron clusters at 12 K

The electronic and far-infrared spectra of nickel and iron clusters trapped in argon matrices at 12 K are reported. The ν3 antisymmetric stretching frequencies for Ni3 and Fe3 were observed for the first time at 198 and 180 cm−1, respectively. The fr and frr force constants for Ni3 are calculated to be 0.80 and 0.13 mdyn/Å, respectively. For Fe3 these are 0.67 and 0.13 mdyn/Å.