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Vector correlation in photodissociation

The vector of the electromagnetic field defines a well specified direction in the laboratory frame relative to which all other vectors relevant in photodissociation can be measured. This includes the transition dipole moment, fi, the recoil velocity of the fragments, v, and the angular momentum vector of the products, j. Vector correlations in photodissociation contain a wealth of information about the symmetry of the excited electronic state as well as the dynamics of the fragmentation. Section 11.4 gives a short introduction. Finally, we elucidate in Section 11.5 the correlation between the rotational excitation of the products if the parent molecule breaks up into two diatomic fragments. [Pg.261]

Houston, P.L. (1987). Vector correlations in photodissociation dynamics, J. Phys. Chem. 91, 5388-5397. [Pg.394]

Another important vector correlation in photodissociation is called v-j correlation, which describes the relationship between the recoil velocity and the angular momentum of one of the fragments. This correlation can give important indications about the kinds of torques in effect between the recoiling products during dissociation. These torques can arise from bending and torsional modes in the parent molecule and from exit channel dynamics. [Pg.288]

G.E. Hall. P. L. Houston Vector Correlations in Photodissociation Dynamics. Annu. Rev. Phys. Chem. 40, 375 (1989)... [Pg.900]

Brouard, M., Martinez, M.T., O Mahony, J., and Simons, J.P. (1988). Photofragment vector correlations in the vibrationally mediated photodissociation of H2O2, Chem. Phys. Lett. 150, 6-12. [Pg.384]

Docker, M.P., Hodgson, A., and Simons, J.P. (1987). High-resolution photochemistry Quantum-state selection and vector correlations in molecular photodissociation, in Molecular Photodissociation Dynamics, ed. M.N.R. Ashfold and J.E. Baggott (Royal Society of Chemistry, London). [Pg.387]

Two basic types of experiments can be preformed with the TOF-MS that will reveal information about the correlated photoproduct distribution. One set of experiments involves the use of the TOF-MS as a velocity analyzer. In this chapter we call this technique as the extraction time-of-flight method. Another type of experiment uses the TOF-MS in its mass resolution mode in conjunction with a two-dimensional ion detector. This technique is known as ion imaging. Variations of these techniques have been developed and are discussed in Section III.B.l.c. Experimentalists have used these methods to measure scalar and vector correlations in many types of photodissociation reactions their results are presented in Section III.B.2. [Pg.303]

These equations enable us to compute aU the possible photofragmentation cross sections. An example of the use of these equations applied to the photodissociation of HOBr may be found in Ref. 84, and similar applications to electronically nonadiabatic photofragmentation of HF, DF, and HCl can be found in Refs. 76, 97, and 96. Time-dependent methods have been used most recently to compute vector correlations and alignment parameters [98,99]... [Pg.264]

Photodissociation dynamics [89,90] is one of the most active fields of current research into chemical physics. As well as the scalar attributes of product state distributions, vector correlations between the dissociating parent molecule and its photofragments are now being explored [91-93]. The majority of studies have used one or more visible or ultraviolet photons to excite the molecule to a dissociative electronically excited state, and following dissociation the vibrational, rotational, translational, and fine-structure distributions of the fragments have been measured using a variety of pump-probe laser-based detection techniques (for recent examples see references 94-100). Vibrationally mediated photodissociation, in which one photon... [Pg.31]

Analysis of the correlations of fi, v, and j with Eo and among each other is necessary for a full understanding of photodissociation dynamics, especially for polyatomic molecules with more than three atoms. Vector correlations play an increasingly important role in experimental investigations. This section covers only the most elementary aspects and for deeper insight the reader is referred to the numerous reviews on this fascinating topic (Zare 1972 Simons 1977 Houston 1987, 1989 Simons 1987 Hall and Houston 1989). [Pg.283]

CO its rotation, must occur such that the angular momentum vector of CO is always perpendicular to the OCS plane, while the recoil direction is always in plane. Therefore, v is perpendicular to j this correlation in OCS photodissociation has in fact been seen [31], The departing CO resembles a tumbling cartwheel. Such vj correlations are very commonly observed. They are expected from the simple impulsive model or indeed from any model where the forces all lie within a plane. Any impulsive force imparted to a diatomic fragment that is directed at a position displaced from the center of mass of the diatomic molecule will lead to both translational and rotational energy and a cartwheeling motion will result. [Pg.289]

Carbon monoxide metastable TOF spectra for ketene photodissociation at 351 nm were taken from jco = 3-18. There was no difference in the shapes of the TOF spectra when the polarization of the probe laser was changed with respect to the flight path. Thus, our results are not sensitive to whatever vector correlations may exist in this photodissociation and the line strength factor of Eq. 38 can be ignored. The resulting F( lrans) functions reveal that... [Pg.338]

This chapter has reviewed recent advances in the measurement of corelation of product states in photodissociation. We have seen that vector correlations are intimately involved with all of these measurements. The ion TOF... [Pg.340]

In a full-collision experiment, e.g. in crossed-beam, beam-gas or gas cell arrangements, the reference axis is the relative velocity vector. Conceptually, the vector correlation is identical to that of photodissociation, only now the relative-velocity vector rather than the electric-field vector defines the symmetry. Thus, the reagents electronic orbital alignment can influence the product yield of a chemical reaction. Imagine, for... [Pg.6]

Figure 22.5 shows a pictorial representation of the so-called two-vector correlation, both in photodissociation (half-collisions) and in atom-exchange reactions (full collisions). The important point to consider is that photodissociation is an anisotropic process in which the polarization of the electric field Sp of the photolysis laser defines a direction with respect to which the vector describing both products and parent molecule can be correlated. As a consequence, one can measure and analyse the correlation between the parent transition dipole moment fi and the recoil photofragment velocity vector, i.e. the v correlation. Thus, the angular distribution of the photofragments I 6) can be described in the form (Zare, 1972)... [Pg.301]


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