Oxygen atoms, excited, deactivation

Excited 0(21D) atoms are metastable and have very long life in the thin upper atmosphere. The atoms are deactivated by energy transfer on Collision with oxygen molecules generating singlet molecular oxygen,... 

The presence of 03 in the troposphere leads to the formation of OH radicals through the photolysis of 03 at wavelengths 290-350 nm to form the electronically excited oxygen atom, 0(JD), which either reacts with water vapor or is deactivated by reaction with 02 and N2 to the ground state oxygen atom, (03P) (Atkinson, 1995 Atkinson et al., 1997). 

Until quite recently, direct measurements of o(>d2)(X) were limited by the very real experimental difficulties associated with the highly efficient deactivation of O ( D2) by O3, as well as the need to provide a sensitive probe for atomic oxygen atoms in the ground Pj state as well as in the electronically excited D2 state. The development of resonance spectroscopic techniques for time-resolved detection of O ( Pi) has permitted monitoring of this state at densities of ca. 10 cm with an instrumental bandwidth in excess of 10 MHz. When combined with the use of high intensity photolysis sources such as the excimer lasers and frequency quadrupled Nd/YAG, it has proved possible to measure directly the yield of 0( D2) and O( Pj) at several discrete wavelengths in the middle ultraviolet. 

Nitrogen. The overwhelming fraction of electronically excited oxygen atoms formed in the photolysis of O3 in the atmosphere are deactivated by collisions with N2 and O2, with kNj [N2]/ko. [O2] = 2.4. This de-... 

The emission from electronically excited atomic and molecular oxygen is the cause of the night airglow. The atmospheric glow originates in the upper atmosphere where the pressure is so low that the radiative decay can compete favourably with the collisional deactivations. 

As explained in Section 16.2.4. fluorescence takes place in competition with radiationless deactivation. Fluorescent emission is normally spherically isotropic and of longer wavelength than the exciting radiation. It is extinguished by heavy atoms in the molecule, by the excitation of free rotation about chemical bonds and torsional vibrations, by high concentrations because of increased collision probabilities, or by the presence of paramagnetic oxygen in the sample solution. This can affect reproducibility in quantitative measurements [28], [84], [127],... 

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