Experimental and theoretical investigations of the reactions NH(X {sup 3}{sigma}{sup -})+D({sup 2}S){yields}ND(X {sup 3}{sigma}{sup -})+H({sup 2}S) and NH(X {sup 3}{sigma}{sup -})+D({sup 2}S){yields}N({sup 4}S)+HD(X {sup 1}{sigma}{sub g}{sup +})
- Max-Planck-Institut fuer Dynamik und Selbstorganisation, D-37073 Goettingen (Germany)
The rate coefficient of the reaction NH(X {sup 3}{sigma}{sup -})+D({sup 2}S){yields}{sup k{sub 1}}products (1) is determined in a quasistatic laser-flash photolysis, laser-induced fluorescence system at low pressures. The NH(X) radicals are produced by quenching of NH(a {sup 1}{delta}) (obtained in the photolysis of HN{sub 3}) with Xe and the D atoms are generated in a D{sub 2}/He microwave discharge. The NH(X) concentration profile is measured in the presence of a large excess of D atoms. The room-temperature rate coefficient is determined to be k{sub 1}=(3.9{+-}1.5)x10{sup 13} cm{sup 3} mol{sup -1} s{sup -1}. The rate coefficient k{sub 1} is the sum of the two rate coefficients, k{sub 1a} and k{sub 1b}, which correspond to the reactions NH(X {sup 3}{sigma}{sup -})+D({sup 2}S){yields}{sup k{sub 1a}}ND(X {sup 3}{sigma}{sup -})+H({sup 2}S) (1a) and NH(X {sup 3}{sigma}{sup -})+D({sup 2}S){yields}{sup k{sub 1b}}N({sup 4}S)+HD(X {sup 1}{sigma}{sub g}{sup +}) (1b), respectively. The first reaction proceeds via the {sup 2}A{sup ''} ground state of NH{sub 2} whereas the second one proceeds in the {sup 4}A{sup ''} state. A global potential energy surface is constructed for the {sup 2}A{sup ''} state using the internally contracted multireference configuration interaction method and the augmented correlation consistent polarized valence quadrupte zeta atomic basis. This potential energy surface is used in classical trajectory calculations to determine k{sub 1a}. Similar trajectory calculations are performed for reaction (1b) employing a previously calculated potential for the {sup 4}A{sup ''} state. The calculated room-temperature rate coefficient is k{sub 1}=4.1x10{sup 13} cm{sup 3} mol{sup -1} s{sup -1} with k{sub 1a}=4.0x10{sup 13} cm{sup 3} mol{sup -1} s{sup -1} and k{sub 1b}=9.1x10{sup 11} cm{sup 3} mol{sup -1} s{sup -1}. The theoretically determined k{sub 1} shows a very weak positive temperature dependence in the range 250{<=}T/K{<=}1000. Despite the deep potential well, the exchange reaction on the {sup 2}A{sup ''} ground-state potential energy surface is not statistical.
- OSTI ID:
- 20722247
- Journal Information:
- Journal of Chemical Physics, Vol. 122, Issue 20; Other Information: DOI: 10.1063/1.1899563; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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