Quantum Yields for NO3 Photolysis between 570 and 635 nm

Article abstract of DOI:10.1021/j100144a017

Quantum yields for the production of O(³P) from the photolysis of NO3 have been measured over the wavelenght range 570-635 nm, using a pulsed laser photolysis-resonance fluorescence technique.Absolute O(³P) quantum yields were determined at selected wavelengths using O3 photolysis to normalize for laser energy and detection sensitivity; the measured quantum yields were 1.06 +/- 0.26 at 582 nm, 0.72 +/- 0.18 at 590 nm, and 0.52 +/- 0.13 at 603 nm.Combining these absolute yields with a series of relative measurements made as a function of wavelength, the O(³P) yield was found to be unity between 570 and 585 nm and to decrease in essentially linear fashion from 585 nm to near zero at 640 nm.Anomalously low O(³P) yields were noted in the strong absorption bands near 623 nm.In addition, NO has been detected as a minor product of NO3 photolysis (quantum yields about 20percent) near 590 nm.The data have been used to calculate atmospheric photolysis rates for (1) NO3 + hυ -> NO2 + O(³P), j₁ = 0.19 s^-1 and (2) NO3 + hυ -> NO + O2, j₂ = 0.016 s^-1.From the wavelength threshold for process 1, the ΔH_f,298 for NO3 was estimated to be 18 +/- 1 kcal/mol.