Brute force orientation

R. Brooks [42-44] the process of electron transfer for K to oriented t-butyl bromide is found strongly dependent on the orientation. Systems involving metal atoms are traditional favorites of molecular beam studies, particularly of stereodynamics. In recent experiments [45], with brute force oriented ICl, experimental determination was made of the cone of acceptance for reactivity (steric effect) in a "harpooning" reaction, Sr + ICl leading to electroiucally excited products detected via their chemiluminescence... 

Loesch, H.J., Moller, J., Steric effects and vector correlations in reactions of K atoms with brute force oriented aromatic molecules. Faraday Discuss. 1999, 113, 241. 

F. Brute force orientation requires cold molecules. Consider a dilute gas of diatomic molecules with a permanent dipole moment /u, in an electrical field E. The interaction energy of an individual molecule witti the field is -fiE cos 9 where 6 is the angle between the dipole and the field. In the ground state the gas is fiilly oriented but the thermal motion allows the occupation of higher-energy states where the dipole does not quite point out in the direction of the field, (a) Using the dimensionless variables jc = cos 9, a = ixE/k T show that... 

The method of optimization is a brute-force search technique. All the possible laminates that can be obtained by changing the individual laminae orientations by 5° increments are candidates for the optimization process. We consider RC7 because this program is widely used and because it is representative of the brute-force search technique. The basic question is because we must carry a certain load, what laminate do we need We have no idea how many layers are required, much less their orientation, but we must start someplace. 

In practice, the number of trial orientations and positions for the phasing model is enormous, so a brute-force search is impractical, even on the fastest computers. The procedure is greatly simplified by separating the search for the best... 

Two routes have been followed in reaction stereodynamics. One is to orient a molecular reactant in space and see how the reaction cross-section varies with the molecular orientation. This direction has been pioneered in molecular beam experiments using focusing of an electric hexapole field to control the molecular orientation [221-223a]. Numerous studies have applied this technique to electron-transfer reactions of alkaline-earth atoms [223b]. This technique is now complemented by the so-called brute force technique, where polar molecules are oriented in extremely strong electric fields [83]. 

In the brute-force technique, for each chosen orientation (0,(p) of B, one diagonalizes the spin-Hamiltonian matrix for a large munber of values of B to find the resonant magnetic-field value. It requires exorbitant computer time, especially... 

The simulated spectrum is computed by the use of eq. (25), wherein the integrals are converted into discrete sums. It is clear from (25) that, in particular, one needs to know the resonant field values for the various transitions, as well as their transition probabilities for numerous orientations of the external magnetic field over the unit sphere over the unit sphere. A considerable saving of computer time can be accomplished if one uses numerical techniques to minimize the number of required diagonalizations of the SH matrix in the brute-force method. That is, when one uses the known resonant-field value at angle (0,(p) to calculate the one at an infinitesimally close orientation, (0 -i- 80, (p + 8(p), known as the method of homo-... 

Loesch, H. X, X Bulthuis, et al. (1996). Molecules oriented by brute force. Europhys. News 27, 12. 

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