Anthropomorphic activities have increased the CO2 concentration in the earth's atmosphere, and this increase has been correlated with an increase in the average temperature of the troposphere. CO2 is also considered as the major source of prebiotic oxygen in the primitive atmosphere of the earth. Given the wavelength dependence of the solar radiation profile and the CO2 photo-absorption cross section, it is widely believed that the most important photochemical sinks of CO2 molecules take place in the vacuum ultraviolet (VUV) region between 90 and 110 nm, which occurs in the thermosphere. Two independent tunable vacuum ultraviolet (VUV) lasers and the time-sliced velocity-map-imaging-photoion (VMI-PI) method are used to study and identify the CO2 photodissociation channels between 101 and 106 nm. Four spin-allowed channels, CO(X1S+) + O(1D), CO(X1S+) + O(1S), CO(a3?) + O(3PJ), and C(3P) + O2(X3Sg-) and one spin-forbidden photoproduct channel, CO(X1S+) + O(3PJ), were directly detected in the present study. The total kinetic energy release (TKER) spectra derived from the photofragment ion images of C and O reveals information about the vibrational and rotational distributions of the counter O2 and CO photoproducts. The angular distributions are used to estimate the timescales for the formation of these various exit channels observed in CO2 photodissociation. The information contained in the present studies is of pivotal importance to the evolution of the early earth atmosphere. Similar CO2 photochemical processes are expected to prevail in other solar system bodies such as comets, Mars and Venus.Acknowledgements : William M. Jackson and Zhou Lu acknowledge the support of the NSF Grant No. CHE-1301501. C. Y. Ng acknowledges the support of DOE Contract DE-FG02-02ER15306.

Unravelling the vacuum ultraviolet photochemical sinks of CO<sub>2</sub> molecules

248th National Meeting (2014)

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Unravelling the vacuum ultraviolet photochemical sinks of CO2 molecules

Unravelling the vacuum ultraviolet photochemical sinks of CO₂ molecules