No abstract

Carbon d~oxide has been ~rradiated with electron pulses at a dose rate of 2 x loz7 eV g-I s-'.The measured carbon monoxide yield IS G(CO) = 7.8 + 0.3. Addit~on of SF6, an electron scavenger, reduces thls y~eld to G(C0) = 4.8 which is the same, w~t h~n the exper~mental error, as the low dose rate yield G(CO) = 4.5 + 0.5. The efiect of SF6 and the difference between the high and low dose rate y~elds IS explained by suppression of dlssociat~ve neutralization of the CzO,+ Ion.

Low-loss optical planar waveguides in YVO 4 produced by silicon ion implantation at low doses J. Appl. Phys. 94, 4708 (2003); 10.1063/1.1604965Monomode, nonleaky planar waveguides in a Nd 3+ -doped silicate glass produced by silicon ion implantation at low doses

. Can. J. Chen~. 56, 1470 (1978).Proton nmr and infrared studies of neat N,N1-dimethylformamidine (DMFA) have shown that the cis isomer 1 is present exclusively and that it undergoes tautomerisni. At 25 C, k,,,,, = 8.2 x 102s-', E, = 41.5 + 1.5 kJ mol-I, AH+ = 39.1 + 1.5 kJ mol-l, and AS' = -57.5 5.0 J mol-' K-I. The tautomerism is proposed to occur through a hydrogen-bonded cyclic dimer. The effects of solvent on the tautonieric rate in DMFA have also been investigated for CD,NH2 and CDCI3 solutions.Potass~uni N,Nf-dimethylformamidide (PDMFA) in CD3NH2 does not exhibit hindered rotation about the single C-N bond on the nmr tlme scale over the temperature range -56 to 25°C. Howevcr, protonated DMFA undergoes hindered rotation about this bond in highly In this series Part I (1) dealt with the thermal decomposition of both potassium methylamide in methylamine solutions (which yielded potassium N,N1-dimethylformamidide (PDMFA)) and the neat free base, N,N'-dimethylformamidine (DMFA). Part I1 (2) discussed the hydrolysis of the D M F A as a function of pH. In the course of these studies several unusual features associated with isomerism (geometricaI, rotational) and tautomerism (3) The solvents CD3NH2 (>98 at.% D ) and CDC13 (> 99.8 at.% D) (Merck, Sharp, and Dohme), the former dried over l i t h i~~m metal, were distilled under vacuum before use. CHC13 (Fisher Spectranalyzed) was used for the infrared measurements. and hir;de;ed rotation in the title compound and its Although there is a reaction between DMFA and C D~N H Z , cationic and anionic forms as functions of solvent eq. [[I (4a), that produces the i s o t o~i c a l l~ labeled mono-a n d di-CD3 DMFA species, it is sufficiently slow that measurements and temperature.of the tautomerisnl in DMFA can be made without appreExperimental ciable deuterium isotope effects interfering.Proton nmr spectra were recorded o n a Bruker HX90 nnlr All nmr san~ples were handled using dry box (He atmos-SPectronIeter operating at 90 MHz ill a field of 2.114 T.Variable temperature studies were performed using a Bruker variable temperature controller, B-ST 100/700 (+0.5"C For personal use only.