Photochemical Gas Phase Reactions in the Hydrogen‐Oxygen System

The Chemistry of Mercury in the Stratosphere

“…The reaction of excited atomic mercury Hg ( 3 P 1 ) with O 2 (R3) has been studied for nearly a century, beginning with Gaviola's pioneering experiments on Hg‐sensitized photochemistry (Gaviola, 1929 ), and reviewed several times (Burton & Noyes, 1969 ; Callear, 1987 ; Callear et al., 1959 ; Noyes & Leighton, 1941 ; Volman, 1963 ). The laboratory experiments show that the final reaction products are O 3 in large quantities (up to 60 molecules for each consumed mercury atom) (Volman, 1963 ) and HgO deposited as a solid film. However, the experiments did not establish unambiguously the path to HgO, and in particular the rate coefficient of the HgO primary reaction (R3a) could not be determined (See Supplementary Information, Part 1 in Supporting Information S1 ).…”

“…The R3b step is just the transfer of electronic energy from atomic mercury to molecular oxygen (Figure S3 in Supporting Information S1 ) with a rate comparable to the collision frequency ( k coll ∼ 10 −10 cm 3 molecule −1 s −1 , 240K) (Callear, 1987 ; Callear et al., 1959 ; Horiguchi & Tsuchiya, 1974 ; Volman, 1963 ). Triplet‐triplet energy transfer experiments (Hippler et al., 1978 ) as well as O 3 synthesis cannot be explained unless the resultant excited oxygen molecule (O 2 * ) is produced in a high‐lying electronic state ( A,C or c (Michels, 1981 )).…”

“…The Hg-O bond-energy obtained in this way (27.3 kJ mol −1 ) is similar to previous predicted values, and in the spin-conserving reaction the mercury oxide would be produced as HgO( 3 Π) with little vibrational energy, ∼6 kJ mol −1 (Supplementry Information and Figure S3 in Supporting Information S1), which is important for such a weakly bound molecule to survive in the stratospheric low-temperature environment. The R3b step is just the transfer of electronic energy from atomic mercury to molecular oxygen (Figure S3 in Supporting Information S1) with a rate comparable to the collision frequency (k coll ∼ 10 −10 cm 3 molecule −1 s −1 , 240K) (Callear, 1987;Callear et al, 1959;Horiguchi & Tsuchiya, 1974;Volman, 1963). Triplet-triplet energy transfer experiments (Hippler et al, 1978) as well as O 3 synthesis cannot be explained unless the resultant excited oxygen molecule (O 2 * ) is produced in a high-lying electronic state (A,C or c (Michels, 1981)).…”

“…The reaction of excited atomic mercury Hg ( 3 P 1 ) with O 2 (R3) has been studied for nearly a century, beginning with Gaviola's pioneering experiments on Hg-sensitized photochemistry (Gaviola, 1929), and reviewed several times (Burton & Noyes, 1969;Callear, 1987;Callear et al, 1959;Noyes & Leighton, 1941;Volman, 1963). The laboratory experiments show that the final reaction products are O 3 in large quantities (up to 60 molecules for each consumed mercury atom) (Volman, 1963) and HgO deposited as a solid film.…”

A review of elemental mercury removal processing

“…One widely studied area and relevant has been the photochemistry oxidation of mercury using 253.7 nm ultraviolet light [30][31][32][33][34][35][36][37]. Dickinson and Sherrill [30] demonstrated the photochemical formation of mercuric oxide via the sensitized formation of ozone in 1926.…”