In the present work, γ-terpinene (a 1, 4-diene derivative) and α-phellandrene (1, 3-diene derivative) were isolated in cryogenic argon matrices and their structures, vibrational spectra, and photochemistries were characterized with the aid of FTIR spectroscopy and quantum chemical calculations performed at the DFT/B3LYP/6-311++ G (d, p) level of approximation. The molecules bear one conformationally relevant internal rotation axis, ...