Theoretical calculations have predicted the existence of metastable O4 molecules with two different shapes: a "puckered" square like cyclobutane, and a "pinwheel" with three oxygen atoms surrounding a central one in a trigonal planar formation similar to Boron Trifloride.
In 2001, a team at the University of Rome La Sapienza conducted a neutralization-reionization mass spectrometry experiment to investigate the structure of free O4 molecules. Their results did not agree with either of the two proposed molecular structures, but they did agree with a complex between two O2 molecules, one in the ground state and the other in a specific excited state.
Remote sensing of particulate pollution from space: have we reached the promised land?(2009 CRITICAL REVIEW)(Report)
Jun 01, 2009; ABSTRACT The recent literature on satellite remote sensing of air quality is reviewed. 2009 is the 50th anniversary of the first...