Methane-water vapor mixtures were irradiated using a low pressure mercury lamp and the reaction products were determined at intervals between 0.5 and 6 hr. Formaldehyde, acetaldehyde, and methanol were observed after 0.5 hr. The presence of ethylene glycol, ethanol, acetone, isopropyl alcohol, tert-butyl alcohol, methyl ethyl ketone, isobutyl alcohol, rert-amyl alcohol, and neopentyl alcohol was detected in small amounts after 2 hr and the yields increased after 4 and 6 hr irradiation times. Virtually the same product yields were obtained after irradiating a -2:l methane-water mixture as were obtained from a -1: 1: 1 methane-nitrogen-water mixture demonstrating that nitrogen does not react under these conditions. Furthermore, no amino acids were detected when nitrogen was added to the reaction mixture. The reactions are initiated by the hydroxyl radicals formed by water photolysis. These hydroxyl radicals abstract a hydrogen atom from methane as the first step in the synthesis. The prebiological significance of these photochemically generated compounds is discussed.Ultraviolet light from the sun offered the greatest potential as the energy source t o drive chemical reactions on the primitive earth. I t has been estimated that, in the absence of ozone, wavelengths less than 300 n m contributed 3400 cal c m W 2 year-' and those less than 200 n m contributed 41 cal cm-2 year-' t o t h e surface of the primitive earth.2 T h e next most abundant energy sources, electrical discharges and shockwaves are estimated to have contributed 4 and 1.1 cal Journal of the American Abstract: The relative cross section for the gas phase photodetachment of electrons has been determined for several substituted phenoxides and thiophenoxide in the wavelength region 300-530 nm (4.1 3-2.34 eV). An ion cyclotron resonance spectrometer was used to generate, trap, and detect the negative ions and a 1000-W xenon arc lamp with a grating monochromator was employed as the light source. The following quantities were determined: EA(o-CH3C6H40.) S= EA(CsH5O.) I 2.36 f 0.06 eV, EA(o-CIC6H40.) I 2.58 f 0.08 eV, EA(C6HsS.) I 2.47 f 0.06 eV. I t is suggested that a short wavelength portion of the photodetachment spectrum is the result of electronic excitation of the negative ions, followed by autodetachment. Recent photodetachment experiments have indicated of molecular properties. The threshold yields a vertical electron detachment energy, which in favorable cases also represents the electron affinity of the corresponding radical. Abrupt changes in the photodetachment cross section can arise from transitions to excited state^,^ thus, transition Brauman et al. / Photodetachment of Electrons f r o m Phenoxides and Thiophenoxide that complex molecular ions can exhibit unusual behavior. This appears to be particularly true for delocalized systems, such as C5H5-and C4H4N-.3%4 The photodetachment cross section of an anion can provide information about a variety
