Vacuum UV photolysis of methylamine

184 Vacuum UV photolysis of methylamine

EDWARD

P. GARDNER

University of Maryland,

and JAMES

Department

R. McNESBY

of Chemistiy,

MD (U.S.A.)

Quantum yields of Hz, CH4, CzHs and N2 were measured for the photolyses of methylamine at 123.6, 147.0 and 184.9 nm. The H2 quantum yields at the three wavelengths are respectively 2.0,2.0 and 1.5. Molecular elimination accounts for 40% of the H3 at 123.6 and 147.0 nm and for less than 7% at 184.9 nm. The mechanism deduced includes the following reactions at 123.6 and 147.0 nm: CH3NH2 -_, 2H + CH2=NH* CH,=NH* + M j CH2=NH2 + M CH2=NH* + HCN* + H2 HCN*+M+HCN+M HCN*-+H+CN At 184.9 nm the mechanism is mainly as follows: CH3NHt + H + C&N* C&N*+M-+CH,N+M CHz,N* --_,H + CH2=NH

Photochemistry

of acetylene at 1470 A

H. OKABE Nutiond

Bureau of Standards,

Washington,

DC 20234

(U.S.A.)

The photolysis of acetylene at 1470 A was studied over the pressure region from 0.1 to 10 Torr. The quantum yield of diacetylene formation was measured as functions of acetylene, helium and nitrogen pressures. The. quantum yield is constant at 0.3 below 0.8 Torr of CzH2 and is independent of nitrogen pressure. It increases to a plateau value of 0.9 above 3 Torr of CzHz where the addition of nitrogen or helium decreases the quantum yield. It is concluded that the major primary photochemical process is a direct dissociation CzH$G

C2H + H

with a quantum yield of 0.3. The remaining process is the formation of a metastable acetylene which either reacts with ground state acetylene to form C2H radicals or is deactivated by collisions with the walls or inert gases. The reaction rate of C2H with hydrogen or methane was measured relative to that with acetylene.