Deuterium molecule

Thermodynamic data on H2, the mixed hydrogen—deuterium molecule [13983-20-5] HD, and D2, including values for entropy, enthalpy, free energy, and specific heat have been tabulated (16). Extensive PVT data are also presented in Reference 16 as are data on the equihbrium—temperature... 

The interaction of hydrogen (deuterium) molecules with a transition metal surface c an be conveniently described in terms of a Lennard--Jones potential energy diagram (Pig. 1). It cxxislsts of a shallcw molecular precursor well followed by a deep atomic chemisorption potential. Depending on their relative depths and positions the wells m or may not be separated by an activation energy barrier E as schematically Indicated by the dotted cur e in Fig. 1. 

Figure 3. Angular distribution of the relative scattered intensity of deuterium molecules scattered from a) Ni(110) b) Ni(111). lite esqierlnental conditions were the same as in Figure 2.

The hydrogen molecule does not chemisorb onto clean sintered gold surfaces at or above 78 K [147] but on unsintered films, a small amount of H2 is chemisorbed if gold surface atoms of low coordination number are present [148]. Stobinski [149] found that H2 can also chemisorb on thin sintered Au films if the surface is covered at low temperatures with a small amount of gold equivalent to 1-3 Au monolayers prior to H2 exposure. This suggests a fundamental role of surface Au atoms of low coordination number in the chemisorption process. Deuterium molecules also chemisorb in a similar fashion on gold films at 78 K and isotope effects were... 

In most cases the photofragmentations were also carried out with the corresponding deuterated isotopomers (see indications in the formula). By this means the structural identification of the new species by comparison between the experimental and calculated spectra became much more reliable. Furthermore it was again possible to register the bands of "complexed" deuterium molecules [16] [23-D2 v = 2994 cm"1 24-D2 v = 3010 / 3005 cm"1]. 

Figure 4. The number of deuterium molecules found in products on Vx clusters produced while attempting to saturate the reaction. The solid lines are plots of D2 V ratios of 1 and 0.5, including all vanadium atoms. The dashed lines are corrected, assuming globular shaped clusters. The best least-squares fit to the data, D2 V = 0.68, is also plotted as a dashed line.

Fig. 6. Spreading resistance and SIMS profile from deuterated CZ Si containing an initial uniform concentration of 6 x 1016 cm-3 thermal donors. The high, near-surface concentration is due probably to deuterium molecule formation (Pearton et al., 1986). 

Farkas and Farkas suggested that the critical step in hydrogenation involved the simultaneous addition of two hydrogen atoms to an adsorbed benzene molecule, whereas exchange with deuterium required the prior dissociation, on the surface, of benzene to form a phenyl radical and a hydrogen atom. The phenyl radical then combined with a deuterium atom, which had been produced by the dissociation of a deuterium molecule, and the monodeuterobenzene was desorbed. 

A deuterium arc lamp has two electrodes, bathed in an atmosphere of deuterium, between which a metallic screen pierced with a hole of 1 mm in diameter is placed. The discharge current creates an intense arc at the level of this hole, which is close to the anode. Under electron bombardment, deuterium molecules dissociate, emitting a continuum of photons over the range of 160 to 400 nm (Fig. 11.9). 

The difference in reactivity was also found for the paramagnetic surface defects -(=Si-0-)3Si radicals [16]. Since the observed effects are due to the difference in the structure of the nearest environment of the surface silicon atom, it is most pronounced when this atom acts as an active site. This difference should cease with an increase in the number of chemical bonds that separate the active site and surface silicon atom of the solid with which it is linked. They are almost absent for the (=Si-0-)3Si-CFl2- CF[2 radical in which the active site is localized on the terminal carbon atom [16]. For this reason, it is desirable to have a probe in the immediate contact with a lattice silicon atom. The Si-H group fits best these requirements. Such groups can be obtained upon the interaction of the silyl-type radicals with the hydrogen or deuterium molecules (cf. Section 6.3). The IR band due to the stretching vibrations of the Si-Fl bonds obtained upon the hydrogenation of silyl radicals ... 

The reaction of sSi-N -H radicals with deuterium molecules occurs in a similar manner. The rates of both processes are proportional to gas pressure over the sample, and the rate constants of these bimolecular reactions at 301 K are fc(H2) = (2.7+ 0.3) x 10 17cm3/molecule/sec and k(D2) = (5.1 + 0.5) x 10 18cm3/molecule/sec. Thus, the value of the isotope effect of this reaction at room temperature is close to 5. 

The radiation of a vibrational band is directly correlated to the vibrational population in the excited state I(v — v") = n(v ) x Av>v . Av>v is the transition probability. Thus, several vibrational bands which originate from different vibrational levels yield the corresponding vibrational population. In case of hydrogen or deuterium molecules the population of the first four or five vibrational levels, respectively, is accessible. Higher vibrational levels are disturbed by pre-dissociation processes. For further analysis, it is very convenient to use the relative vibrational population n(v )/n(v = 0). 

Deuterium labelling combined with deuterium decoupling is well known as a method in spectral analysis and in stereochemical and conformational studies. The deuterium-decoupled proton spectra of XCHD.CHDY compounds produced during mechanistic studies are useful for determining the stereochemical course of reactions such as the methoxymercuration of ethylene, (478) the conversion of tyramine into tyrosol, (479) the non-catalytic addition of deuterium molecules to cyclopentadiene, (480) and alkyl transfer and olefin elimination in 2-phenyl-l,2-dideuterioethyl transition metal compounds. (481) The proton spectra of [ H ]- and [ Hg]-t-butylcyclohexanes were... 

The absence of any effect of deuterium on the rate of reaction and the small extent of deuterium incorporation in the products with CeX suggest that the mechanism is ionic rather than radical. The small amounts of exchange noted could result from the very strong electrostatic fields associated with the Ce " ion causing some heterolytic splitting of the deuterium molecule. In contrast, the enhanced isomerization rates exhibited in the presence of D2O provide added confirmation of the protonic activity of these catalysts, as also does the substantial amount of deuterium incorporation. As Table III indicates, the majority of exchange takes place with the products and is therefore assumed to result from the isomerization process. 

Deuterium ( H), when heated to sufficiently high temperature, undergoes a nuclear fusion reaction that results in the production of helium. The reaction proceeds rapidly at a temperature, T, at which the average kinetic energy of the deuterium atoms is 8 X 10 J. (At this temperature, deuterium molecules dissociate completely into deuterium atoms.)... 

It is of importance to note that, except for hydrogen and deuterium molecules, the entropy derived from heat capacity measurements, i.e., the thermal entropy, as it is frequently called, is equivalent to the practical entropy in other words, the nuclear spin contribution is not included in the former. The reason for this is that, down to the lowest temperatures at which measurements have been made, the nuclear spin does not affect the experimental values of the heat capacity used in the determination of entropy by the procedure based on the third law of thermodynamics ( 23b). Presumably if heat capacities could be measured right down to the absolute zero, a temperature would be reached at which the nuclear spin energy began to change and thus made a contribution to the heat capacity. The entropy derived from such data would presumably include the nuclear spin contribution of R In (2i + 1) for each atom. Special circumstances arise with molecular hydrogen and deuterium to which reference will be made below ( 24n). 

This lack of HD production during the decomposition of GeH4 -f Dg rules out a Eley-Rideal mechanism, involving collisions of deuterium molecules in the gas phase (or those in the van der Waals adsorption layer) with the chemisorbed species on the surface. 

We have begun an initial set of computations for pair distribution analysis of our data with the hope that specific correlations can be drawn regarding the precise location (if any) of the deuterium molecules. In any event, these data do show deviations between 35 degrees Kelvin data sets for vacuum and deuterided KC24 as shown in Figure 4. These deviations begin beyond the 5.35 A spacing of the... 

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