Seeded molecular beam

It has additionally been shown to be the predominant reaction route in the case of Xe Cl2 van der Waals complexes generated in seeded molecular beams (Boivineau et al. 1986a,b). 

DePaul S, Pullman D and Friedrich B 1993 A pocket model of seeded molecular beams J. Phys. Chem. 97 2167-71... 

Microwave measurements of uracil in a heated cell suggested the diketo form as the most abundant [54]. Brown et al. reported the first microwave measurements in a seeded molecular beam and also concluded that the diketo form was predominant [55]. Viant et al. reported the first rotationaUy resolved gas phase IR spectra of uracil [28]. This work employed a slit nozzle, an IR diode laser, and a multipass arrangement to obtain high resolution IR absorption spectra of the out-of-phase V(, C2—0, 4=0) stretching vibration. The rotational analysis unambiguously assigned the species to the diketo tautomer. Brown et al. also observed the diketo form of thymine in a seeded molecular beam, based on the hyperfine structure in the 14440-133,11 transition [56]. 

Brown et al. [73] also observed the diketo form of thymine in a seeded molecular beam, based on the hyperfine structure in the 14 jj transition. 

The spectrometer is fitted with a skimmed c.w. supersonic molecular beam source. Many chiral species of interest are of low volatility, so a heated nozzle-reservoir assembly is used to generate, in a small chamber behind a 70-pm pinhole, a sample vapor pressure that is then seeded in a He carrier gas as it expands through the nozzle [103], Further details of this apparatus are given elsewhere [36, 102, 104],... 

Supersonic molecular beam (SMB) mass spectrometry (SMB-MS) measures the mass spectrum of vibra-tionally cold molecules (cold El). Supersonic molecular beams [43] are formed by the co-expansion of an atmospheric pressure helium or hydrogen carrier gas, seeded with heavier sample organic molecules, through a simple pinhole (ca. 100 p,m i.d.) into a 10 5-mbar vacuum with flow-rates of 200 ml. rn in. In SMB, molecular ionisation is obtained either through improved electron impact ionisation, or through hyperthermal surface ionisation... 

A schematic diagram of a state-of-the-art molecular beam-surface machine is shown in Figure 3.10. In this machine, atomic/molecular beams impinge on a clean well-ordered single-crystal surface. Typically, seeded supersonic molecular... 

Molecular beam techniques have been used mostly with small molecules, and most of the information about the dynamics of elementary photochemical processes are restricted to such species. It is however also possible to bring relatively large molecules (e.g. aromatics) into molecular beams through seeding in a carrier gas such as He. 

The study of the reactions of excited species is becoming an increasingly important area of research in kinetics [49, 50]. The excitation may take the form of enhanced translational, rotational, vibrational or electronic energy. Reactions with translational excitation are most commonly studied under molecular beam conditions using seeded nozzle beams or other types of sources to provide the enhanced energy [51, 52]. Translationally hot atoms may also be generated by nuclear recoil [53] or photodissociation [ 54 ]. 

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