Dideuterium

Pulsed lasers such as Nd YAG and excimer lasers are commonly used for the pump-probe experiment just mentioned. Some characteristics of these lasers are listed in Table 3-1. Although the fundamental of the Nd YAG laser is at 1,064 nm, this frequency can be multiplied by using nonlinear crystals, such as KDP (potassium dideuterium phosphate), to obtain the second (532 nm), third (355 nm) and fourth (266 nm) harmonics. Furthermore, a wide range of UV-visible pulsed radiation can be generated from th se harmonics by pumping a dye laser or using a Raman shifter (Sectior 2.2.5). 

Figure 5 Schematic diagram of an experimental set-up for the state-selective study of laser-induced desorption. KDP potassium dideuterium phosphate crystal, BBO p-barium borate crystal, MCP microchannel plate [11].

Only dinitrogen reduction is inhibited by dihydrogen or dideuterium. 

In the presence of dideuterium and dinitrogen, HD is produced in a reaction which uses one electron to form each HD. 

Intermediates in the Fixation of Dinitrogen. There are still no spectroscopically detected intermediates in the reduction of dinitrogen to ammonia. We believe, however, that the electron balance studies with nitrogenase under dinitrogen/dihydrogen and dinitrogen/dideuterium atmospheres point to the existence of such intermediates. The stoichiometry for the HD formation reaction as determined experimentally is shown in Reaction 6. At first glance, this resembles the substrate reactions... 

The reaction with dideuterium is shown in the lower part of Figure 3. Here, the inhibition of nitrogen fixation leads to the production of HD according to Reactions 8 and 9. Clearly, the overall process agrees pre-... 

Finally, the hydrazine reduction reaction is unaffected by either dihydrogen or dideuterium, i.e., under either, there is no inhibition of ammonia formation, and under dideuterium, there is no HD production. Assuming that bound hydrazine reacts in the same manner as added hydrazine, then the dihydrogen and dideuterium effects must occur prior to the formation of bound hydrazine, and again a diimide-level species is implicated. 

SYNS DEUTERIUM OXIDE DIDEUTERIUM OXIDE HEAVY WATER-d2 WATER-d2 (9CI) WATEr2-H2... 

Sialosides have a distinct mechanism of hydrolysis for its unusual sugar structure of sialic acid. For example, the large 8-dideuterium and small primary kinetic isotope effects observed at the anomeric carhon and the large secondary kinetic isotope effect observed at the carboxylate carbon in the acid-catalyzed solvolysis of CMP-Af-acetyl neuraminate 24 support an oxocarbenium ion-like transition state 25 having the 5S conformation without nucleophilic participation of carboxylate and with the carboxylate anion in a looser environment than in the ground state [15] (O Fig. 3). Such a zwitterion structure is consistent with the results from calculations using the COSMO-AMI method for aqueous solutions [16]. 

Perhaps the most likely immediate commercial application of carbonyl fluoride, however, arises from its spectroscopic properties. Irradiation of mixtures of COF, and H, (or D,), over a wide pressure range and at ambient temperature, with the multiline output of a continuous wave CO, laser, results in the generation of excited state HF (DF) which lases [1387]. Energy transfer from the R, line (970 cm" ) of CO, (which is close in energy to the c, band of COF,) causes the dissociation of the COF, to CO and two excited state fluorine atoms which subsequentiy react with the dihydrogen (or dideuterium). However, COF, itself has been found to effect rapid vibrational de-excitation of HF [239], an observation that suggests that the COF,/H, route to the HF laser may be of limited practicality. 

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