PREPARATIVE UV‐LASER PHOTOCHEMISTRY OF THE AZOALKANE SPIRO(2,3‐DIAZABICYCLO(2.2.1)HEPT‐2‐ENE‐7′,1‐CYCLOPROPANE): TRAPPING OF THE 1,4‐DIRADICAL 2‐(3‐CYCLOPENTENYL)ETHYL BY MOLECULAR OXYGEN