ITHACA, N.Y. -- Mario Molina, one of three atmospheric chemists to share the 1995 Nobel Prize, will deliver a Chemistry Colloquium at Cornell University on April 4 at 4:40 p.m. in Room 200 Baker Lab.

His lecture, "The Chemistry of Polar Ozone Depletion," is free and open to the public. It is sponsored by the Cornell Chemistry Department.

Molina, professor of chemistry at the Massachusetts Institute of Technology, shared the Nobel Prize with Paul Crutzen of the Max Planck Institute for Chemistry and F. Sherwood Rowland of the University of California at Irvine, for their pioneering work over more than two decades on the atmospheric effects of the chlorofluorocarbons (CFCs), which they showed to be responsible for the depeletion of stratospheric ozone.

In 1974, Molina, then a postdoctoral fellow with Rowland at California, first described how chemically inert CFCs are wafted into the stratosphere where they are broken up by ultraviolet (UV) radiation in a process called photodissociation. Molina and Rowland closely calculated the mean atmospheric lifetimes of typical CFCs and deduced the catalytic role of the released chlorine atoms in the destruction of ozone molecules.

In addition, Molina's investigations clearly outlined the threats posed by continuing use and production of industrial CFCs common in refrigerants and aerosol propellants -- threats which included a projected ozone depletion of 7 percent to 13 percent at the 1974 rate of production, accompanied by an increase in UV radiation. Use of CFCs as propellants was banned in the United States in 1978, and the three chemists were awarded the Nobel Prize on the eve of the 1996 ban of all ozone-depleting chemicals as mandated in the 1987 Montreal Protocol.

Molina now is studying the effects of CFCs in the northern hemisphere, including the impact of chlorine emissions from a proposed fleet of supersonic transports currently being tested by NASA, and the effects of volcanic particulates on atmospheric ozone. A native of Mexico City, Molina received a Ph.D. in physical chemistry from the University of California at Berkeley in 1972 and, after a postdoctoral season at Irvine, became a senior research scientist at the Jet Propulsion Laboratory at the California Institute of Technology. He joined the MIT faculty in 1989.