Crossed molecular beam apparatus

Figure B2.3.7. Schematic apparatus of crossed molecular beam apparatus with synclirotron photoionization mass spectrometric detection of the products [12], To vary the scattering angle, the beam source assembly is rotated in the plane of the detector. (By pemrission from AIP.)...

Yang X, Lin J, Lee Y T, Blank D A, Suits A G and Wodtke A M 1997 Universal crossed molecular beams apparatus with synchrotron photoionization mass spectrometric product detection Rev. Sc/. Instrum 68 3317-26... 

Fig. 3. A schematic view of a crossed-molecular beam apparatus used for studying the reactions of chlorine atoms with halogen molecules. The mass spectrometer detector is rotatable about the scattering centre for measuring the angular distributions of the reaction products whose recoil velocities are determined by time-of-flight analysis. (Reproduced from ref. 558 by permission of the authors and the American Institute of Physics.)...

The scattering dynamics experiments done in our laboratory utilize the coupling of a laser detonation source (described above) with a crossed molecular beams apparatus (Fig. 0). 42-144 pulsed beam containing energetic species (oxygen atoms or inert species, such as Ar and N2) is... 

FIGURE 14.1 Schematic top view of the crossed molecular beam apparatus. The two pulsed beam source chambers and the detector (electron impact + quadrupole mass filter) rotating chamber are visible. In the case of the CN radical beam source, the carbon rod holder and the incident laser beam are also sketched. The chopper wheel and the cold shield are also shown. 

The major features of the crossed molecular beams apparatus used in these studies have been described elsewhere (21-22). However, several important modifications were made specifically for these studies. The major objectives were to reduce the velocity spread of the reactant beams in order to resolve the product vibrational states as distinct peaks in time of-flight measurements and to reduce the background of mass 20 in the detector, especially near the F atom beam. A scheoiatic top cross sectional view of the experimental arrangement is shown in Figure 2. 

Fig. 1. Schematic diagram of a crossed molecular beam apparatus. (1) primary beam oven. (2) velocity selector. (3) secondary beam oven. (4) velocity analyser for the secondary beam, (5) detector for measuring the differential cross section, (6) monitor detector. (7) detector for measuring the total cross section.

A crossed molecular beam apparatus was described for the study of chemiluminescent reactions such as Fj -I- I2 and Brj -I- Cl2. The effects of collision energy and beam pressure on the chemiluminescence were evaluated. A fast-flow system has been utilized for investigation of bimolecular reactions with rates up to 5 X 10 mol cm s " For an illustration of the method, the kinetics of the chemiluminescent reaction of H3B.N(CHj)3 with 0( P) atoms were determined. Other reactions that have been investigated using chemiluminescence include -f CO and the quenching of 0( Z)) by NjO and Chemilumines-... 

Figure B2.3.3. Crossed-molecular beam apparatus employed for the study of the F + D2 -> DF + D reaction. Indicated in the figure are (1) the effusive F atom source (2) slotted-disk velocity selector (3) liquid-nitrogen-cooled trap (4) D2 beam source (7) skimmer (8) chopper (9) cross-correlation chopper for product velocity analysis and (11) rotatable, ultrahigh-vacuum, triply differentially pumped, mass spectrometer detector chamber. Reprinted with permission from Lee [29]. Copyright 1987 American Association for the Advancement of Scienee. 

Figure 5. Schematic of the crossed molecular beam apparatus (16. ...

FIGURE 11 Schematic diagram of crossed molecular beam apparatus. Beams cross at right angles products are detected by a detector that may be rotated with respect to the reactant beams. 

This thesis will be organized as follows The Chap. 2 describes the H atom Rydberg tagging time-of-flight crossed molecular beam apparatus and experimental methods in our laboratory the Chap. 3 shows the research of resonance phenomenon in the F -I- H2 reaction in the Chap. 4, the breakdown of the B-O approximation in the F - - H2 reaction is introduced. 

Hydrogen Atom Rydberg Tagging Time-of-Flight Crossed Molecular Beam Apparatus... 

Vacuum system of the HRTOF crossed molecular beam apparatus consists of three parts, as shown in Fig. 2.7 source 1 chamber, source II chamber and the main chamber. Two source chambers are connected to the main chamber through respective skimmer, and the two source chambers are completely isolated. The drawings of vertical and horizontal cut view of the chamber are shown in Figs. 2.8 and 2.9. 

Figure 7.16 Typicalbeam-gas or crossed molecular beam apparatus, with one or two (pump/probe) tuneable lasers LIF observation of both reagents and products is prepared, at 45° to the particle/laserbeam axes...

Figure 24.20 Schematic view of the crossed molecular-beam apparatus to study reactions of metal complexes deposited at the surface of large-size clusters. Reproduced from Mestdagh etal, Int Rev. Phys. Chem., 1997, 16 215, with permission...

Both methods require a crossed molecular beam apparatus with high angular and velocity resolution in order to separate the different contributions. It is noted that the scattering process with He transfers a small amount of energy to the cluster which can be measured by analyzing the scattered clusters by time—of—flight methods. ... 

Vohralik and Millerl used a crossed molecular beam apparatus to study HF-HF collisions. Laser excitation was used to state select one beam, and the depletion of the excited state gave evidence of resonant rotational energy transfer. Using a kinetic model involving the reasonable assumption that exactly resonant R-R processes dominate the depletion process, they obtained cross sections for one- and two-quantum resonant R-R processes, HF(ji) + HF(j2) - HF(j2) + HF(ji). Their results are given in Table VI. 

In Sec. 8.2 we discussed the production of cold molecules from a single collision with an atom. It was noted that the cold molecules are necessarily formed at the crossing of the atomic and molecular beams, where the scattering occurs. To date we have put considerable effort to understanding the practical and experimental limits of the crossed molecular beam apparatus for producing cold molecules and what modifications we need and can make in order to produce and confine useful amounts of cold molecules generated from this kinematic cooling technique. 

Figure 13.22 A Crossed-Molecular Beam Apparatus (Schematic). From R. D. Levine and R. B. Bernstein, Molecular Reaction Dynamics and Chemical Reactivity, Oxford University Press, New York, 1987, p. 234.

Tbnekura, N., C. Gebauer, et al. (1999). A crossed molecular beam apparatus using high-resolution ion imaging. Rev. Sci. Instrum. 70, 3265. 

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