Solar photon flux

If Ng(X) is the incident solar photon flux in the wavelength band from X to X + dX (in photons m"2 s"l nm l) and a(X) is the absorption coefficient of the absorber in the same band, then the absorbed flux of photons with X Xg is given by... 

The photodissociation rate coefficients are included as source and sink terms in a system of time-dependent continuity equations for the atmosphere. Modem values for vertical (eddy) diffusion and solar photon flux are utilized. The system of 2nd-order ordinary differential equations is solved by integration, and yields chemical species abundances as a function of time and altitude. The isotope atmospheric chemistry includes only SO2 isotopologue photodissociation reactions and production of SO isotopologues. Additional isotopic reactions such as SO2 oxidation by OH, SO photolysis, SO disproportionation during self-reaction, and SO dimmer formation, have been neglected. My objective here is to focus only on SO2 photolysis as a S-MIF mechanism. 

Js° photons s incident solar photon flux of all wavelengths... 

The amount S of solar photon flux that is absorbed by the colorant per unit area is defined (integrated from zero to the ozone cut-off) ... 

Table A-3. Average Solar Photon Flux Outside Earth s Atmosphere According to Data of Samain and Simon (1976) and Neckel and Labs (1981)...

The objectives of the study presented in this paper were to observe and characterize phototransients produced by laser excitation of natural waters and humic substance (HS) solutions. The photosystems were studied on two scales. On the laboratory scale pulsed laser flash photolysis was used to study the time resolved and spectral behavior of the photochemical transients. Studies to Identify and quantify the transients Included adding energy and electron acceptors and model compounds to the solution and varying parameters such as pH, metal, and oxygen content. On the field scale laboratory data taken at solar actinic wavelengths Is extrapolated using published solar photon fluxes to predict environmental effects of the phototransients studied In this work. This paper thus contains an overview of many experiments performed over four years (16). 

The quantum yield calculated from laser data for solvated electron production by Aldrich HSX excited at 355 nm was extrapolated to a day averaged surface steady state concentration of solvated electron n sunlit waters. In direct sunlight an average rate of 1.62 X 10 photons per second Impinging on a square centimeter of surface water was calculated from solar photon fluxes (32-33). Using absorptlvltles of HS from 299 to 800 nm (with an O.D. of 0.1 at 355 nm) and a solvated electron production quantum yield of 0.014 (16), a rate of 3.50 x 10 moles of solvated electrons produced per second was calculated. Based on a lifetime of 0.25 microseconds for solvated electrons In air saturated natural waters, the surface steady state concentration the top coble centimeter of water was calculated to be about 10 M. 

---