Vibrationally Excited Nitric Oxide Produced in the Flash Photolysis of Nitrosyl Chloride

Nature ◽  
1961 ◽  
Vol 189 (4763) ◽  
pp. 455-456 ◽  
Author(s):  
N. BASCO ◽  
R. G. W. NORRISH

From measurements of the absolute concentrations of vibrationally excited oxygen produced in levels v" = 4 to v" = 13, it is concluded that ca . 20 % of the exothermicity of the reaction O( 3 P) + NO 2 → NO + O + 2 ( v" ≤11) (1) appears initially as vibrational energy in oxygen. Vibrationally excited nitric oxide ( v" = 1, 2) is also observed and may be produced in this reaction or in the primary process NO 2 + hv → NO ( v" ≤ 2) + O( 3 P). More highly excited oxygen ( v" ≤ 15), with energy exceeding the exothermicity of the reaction, is produced in reaction (1) when the NO 2 is first excited by radiation above the dissociation limit near 400 nm. The excited NO 2 thus produced can also transfer energy to nitric oxide. NO 2 * + NO( v" = 0) → NO 2 + NO( v" = 1).



The flash photolysis of nitrosyl chloride and nitrosyl bromide has been studied under isothermal conditions. Vibrationally excited nitric oxide molecules were produced and all levels from v " = 0 to v " = 11 were observed in absorption from the ground electronic states in the β, γ, δ and Є systems. Some of these bands have not previously been reported. The mechanism of the production is either directly NO R + hv → NO ( X 2 II , v ≤ 11) + R ( 2 P ), or by the sequence which includes the reactions NO R + hv → NO( 4 II ) + R , NO. 4 II + M → NO ( X 2 II , v > 0) + M In the latter case, the 4 II state of NO lies not more than 3·5 eV above the ground state. Other possible mechanisms and models accounting for the direct production of vibrationally excited NO in its ground electronic states are discussed. By flashing chlorine in the presence of NOCl it was shown that the reaction Cl + NOCl → Cl 2 + NO ( v > 0) does not occur, thus providing direct evidence that in reactions of the type A + BCD → AB + CD only the AB molecule containing the newly formed bond can be vibrationally excited. Vibrational relaxation is very rapid and probably occurs by step-wise degradation involving resonance vibrational energy transfer. NOCl and NOBr are very efficient and with NO itself the reaction NO ( v = n ) + NO ( v = 0) → NO ( v = n -1) + NO ( v = 1) can be followed.





The flash photolysis of sulphur dioxide under adiabatic conditions results in the complete temporary disappearance of its spectrum , which then slowly regains its original intensity over a period of several milliseconds. Simultaneously with the disappearance of the sulphur dioxide spectrum a continuous absorption appears in the far ultra-violet and fades slowly as the sulphur dioxide reappears. It is shown that the effect of the flash is thermal rather than photochemical, and the possibility of the existence of an isomer of sulphur dioxide at high temperatures is discussed; the disappearance of the normal spectrum on flashing is explained in this way. Several previously unrecorded bands of SO observed in the photolysis indicate that the vibrational numbering of its spectrum should be revised by the addition of 2 to the present values of v' . This leads to a value of the dissociation energy of 123.5 kcal. In formation about the levels v' = 4, 5 and 6 has also been obtained. The isothermal flash photolysis of sulphur trioxide results in the appearance of vibrationally excited SO, and the primary photochemical step in this reaction is discussed.



2020 ◽  
Author(s):  
Zachary D. Buen ◽  
Casey Broslawski ◽  
Madeline Smotzer ◽  
Jason E. Kuszynski ◽  
Simon North ◽  
...  




2007 ◽  
Vol 129 (17) ◽  
pp. 5621-5629 ◽  
Author(s):  
Changjian Feng ◽  
Gordon Tollin ◽  
James T. Hazzard ◽  
Nickolas J. Nahm ◽  
J. Guy Guillemette ◽  
...  






2005 ◽  
Vol 34 (6) ◽  
pp. 752-753
Author(s):  
Simona N. Bengea ◽  
Yasuyuki Araki ◽  
Osamu Ito ◽  
Jotaro Igarashi ◽  
Hirofumi Kurokawa ◽  
...  


Sign in / Sign up

Export Citation Format

Share Document