Determination of the absolute photolysis cross section of sodium superoxide at 230 K: Evidence for the formation of sodium tetroxide in the gas phase

Journal Article · Thu Oct 19 04:00:00 EDT 1989 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100358a030· OSTI ID:6825308

Rajasekhar, B; Plane, J M.C. ^[1]; Bartolotti, L ^[2]

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1. Univ. of Miami, FL (USA)
2. Univ. of Miami, Coral Gables, FL (USA)

The absolute cross section for the photodissociation process NaO{sub 2} + hv {yields} Na + O{sub 2} has been measured at 230 K by the technique of pulsed excimer laser photolysis of NaO{sub 2} followed by laser-induced fluorescence of the resulting Na fragment, yielding {sigma}(193 nm) = (4.0 {plus minus} 2.1) {times} 10{sup {minus}18} cm{sup 2}, {sigma}(248 nm) = (3.9 {plus minus} 2.2) {times} 10{sup {minus}18} cm{sup 2}, and {sigma}(308 nm) = (1.7 {plus minus} 1.0) {times} 10{sup {minus}18} cm{sup 2}. These results are interpreted by ab initio calculations on the excited electronic states of NaO{sub 2} and by reference to the matrix-isolated UV absorption spectrum of NaO{sub 2}, which indicate that photodissociation occurs via excitation from the ground {sup 2}A{sub 2} state to three {sup 2}B{sub 1} states, with absorption maxima at 309, 248, and 163 nm. The lowest excited state correlates with Na({sup 2}S) + O{sub 2}({sup 3}{Sigma}{sub g}{sup {minus}}), and the upper states correlate with Na({sup 2}S) + O{sub 2}({sup 1}{Delta}{sub g}). The photodissociation cross section from 150 to 400 nm is derived and employed to calculate a photolysis rate of J(NaO{sub 2}) = (4.8 {plus minus} 2.9) {times} 10{sup {minus}3} s{sup {minus}1} in the upper atmosphere above 70 km. The atmospheric significance of this rate is discussed. The experimental study also indicates that another sodium oxide is formed, with a significantly larger cross section at {lambda} = 248 nm. We conclude that this is NaO{sub 4}. A discussion of its stability and ab initio calculations of its possible structure are presented.

• OSTI ID: 6825308
• Journal Information: Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 93:21; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKALI METAL COMPOUNDS
CALCULATION METHODS
CHALCOGENIDES
CHEMICAL REACTIONS
CROSS SECTIONS
DATA
DATA ANALYSIS
DECOMPOSITION
ENERGY LEVELS
EXCITED STATES
EXPERIMENTAL DATA
INFORMATION
LOW TEMPERATURE
MEASURING INSTRUMENTS
MEASURING METHODS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
SODIUM COMPOUNDS
SODIUM OXIDES