in solid matrix Irradiation (UV/VIS); quartz UV cell, degassing by three freeze-pump-thaw cycles, placing the cell into a quartz windowed Dewar filled with liquid N2, irradn. with a low-pressure mercury lamp (254 nm) at 77K for 5-30min., warming to room temp., recooling to 77K, 3-MP matrix; not isolated, detd. by UV;