Reaction of Monoenergetic Deuterium Atoms with Hydrogen and Monoenergetic Hydrogen Atoms with Per-Deutero Methane

Author: Betts, Jeanette Asay

Year: 1971

Degree: Dissertation (Ph.D.)

Advisor: Kuppermann, Aron

Committee Member: Unknown, Unknown

Option: Chemistry

DOI: 10.7907/8E5X-D717

Abstract

Mixtures of DBr-H2, DI-H2 and HBr-CD4 were photolyzed with monochromatic light. Thirteen different wavelengths were used in the DBr-H2, DI-H2 systems yielding deuterium atoms with initial laboratory energies ranging from 0.6 to 3.0 eV. We were able to obtain the integral reaction yield

AH + D2 = k1/k1 + k2

where k1 and k2 are effective bimolecular rate coefficients for the process:

D* + H2 → DH + H (1)

D* + H2 → D + H2 (2)

These processes describe rates of reaction and thermalization which accompany the injection of monoenergetic atoms into thermal H2 gas. We were also able to obtain the integral reaction yield for the H + CD4 system at five wavelengths with initial H atom laboratory energies ranging from 1.15 to 3.0 eV.

For both the D + H2 and H + CD4 systems we were able to show that the integral reaction yield is a monotonically increasing function of energy over the energy ranges scanned. For D + H2 a ranged from 0 at about 0.6 eV to 0.66 at 2.86 eV initial laboratory energy while for H + CD4 A ranged from 0.015 at 1.15 eV to 0.040 at 3.0 eV initial laboratory energy. There is an order of magnitude difference between the integral reaction yields for H + CD4 and either D + H2 or H + D2. These differences were attributed to the greater probability of inelastic collisions occuring in the H + CD4 system than in the D + H2 or H + D2 systems. Finally, we were able to show how reaction cross sections can be extracted from the experimental integral reaction yield using a steady state Boltzmann equation.

We were also able to measure the abstraction fraction a for the reaction of H with DX (X = Br, I). The results were a(DBr) = 0.99 ± 0.03 and a (DI) = 0.97 ± 0.05.

Finally, using the integral reaction yield versus energy plot for D + H2 plus additional DI-H2, DI-He experiments we were able to determine the fraction f of iodine atoms produced in the excited 2P1/2 state in the photolysis of DI at 4 wavelengths. The results are f(2800Å) = -0.08 ± 0.27, f(2537Å) = 0.46 ± 0.05, f(2400Å) = 0.60 ± 0.07 and f(2138Å) = 0.33 ± 0.1.

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