UV photochemistry of 1,3-cyclohexadiene isolated in solid parahydrogen

•Photochemistry of 1,3-cyclohexadiene in solid parahydrogen were investigated by a joint use of infrared spectroscopy and density functional theory calculations.•The trans-E-trans-1,3,5-hexatriene and trans-Z-trans 1,3,5-hexatriene as main, and the cis-Zcis-1,3,5-HT, which is a start molecule of the ring-opening reaction of 1,3-CHD, are observed as the photoproducts of 1,3-cyclohexadiene by 193 nm light irradiation.•The bicyclic molecules, bicyclo[2.2.0]hex-‑2-ene and 1-methyl-bicyclo[2.1.0]pent‑2-ene, are also produced by photochemical ring-closing and ring-opening reaction of 1,3-cyclohexadiene.