Intramolecular dynamics of highly

IV. Intramolecular Dynamics of High Rydberg States in Polyatomic Molecules... 

IV. INTRAMOLECULAR DYNAMICS OF HIGH RYDBERG STATES IN POLYATOMIC MOLECULES... 

The Intramolecular Dynamics of Highly Excited Carbonyl Sulfide (OCS)... 

With respect to our understanding of the fundamental intramolecular dynamics of highly vibrationally excited molecules, intrincsic non-RRKM behavior is more significant than is apparent non-RRKM behavior. Intrinsic non-RRKM behavior exists when there are vibrational states weakly coupled to the reaction coordinate so that uni-molecular decomposition does not have a random probability. Closely related to intrinsic non-RRKM behavior is the presence of long-lived vibrational states in highly excited molecules. This is discussed in the next section. 

Classical trajectory calculations have given some support to the local mode model. Trajectories for the H-C-C H + C=C system are quasiperiodic in an internal coordinate representation. A classical trajectory study of the intramolecular dynamics of highly excited CH bonds in benzene shows that energy remains localized in CH bonds on a picosecond time scale.Deuteration destroys this result, presumably as a result of increased momenta coupling (larger g terms) for CD bonds as compared to CH bonds. Also, the decomposition of model H-Si-Si is found to be more intrinsically non-RRKM than is H-C-C decomposition. This result is consistent with decreased local mode momenta coupling for H-Si-Si. 

Reddy, K. V., Heller, D. F., and Berry, M. J. (1982), Highly Vibrationally Excited Benzene Overtone Spectroscopy and Intramolecular Dynamics of CsH6, C6D6, and Partially Deuterated or Substituted Benzenes, J. Chem. Phys. 76, 2814. 

A detailed understanding of the intramolecular motion of highly excited molecules is important for understanding the dissociation dynamics, because the sequences of bound states just below the dissociation threshold continue as resonances to energies above the threshold [52]. Whether the dynamics around the threshold is chaotic or whether the eigenstates show characteristic feamres will have consequences for the lifetime of the excited complex and therefore on the dissociation rate. The same is true, of course, also for the inverse process— that is, the stabilization of complexes in collisions with gas atoms. 

Spin and fluorescent labelling experiments on intramolecular dynamics of hyperthermostable -glycosidase indicate a higher rigidity of the enzyme protein globule as compared with the relevant non-thermostable enzymes, as well as clear-cut correlation between conformational mobility and the catalytic activity of the enzyme active site at high temperature (90-100° C)... 

In this brief overview no attempt is made to survey the vast amount of literature pertaining to the intramolecular and unimolecular dynamics of highly excited molecules. Instead a discussion is given of recent developments and how they effect our understanding of unimolecular reactions. This overview is primarily limited to unimolecular reactions in the ground electronic state. However, when appropriate, reference is made to the intramolecular and unimolecular dynamics of excited electronic states. For comprehensive discussions of unimolecular reactions readers are referred to the recent articles by Rice, Hase, Quack and Troe, McDonald, Chesnavich and Bowers, Oref and Rabinovitch, and Holmes and Setser, and the books by Robinson and Holbrook, and Forst. ... 

Experimental studies of liquid crystals have been used for many years to probe the dynamics of these complex molecules [12]. These experiments are usually divided into high and low-frequency spectral regions [80]. This distinction is very important in the study of liquid crystalline phases because, in principle, it can discriminate between inter- and intramolecular dynamics. For many organic materials vibrations above about 150 cm are traditionally assigned to internal vibrations and those below this value to so-called lattice modes . However, the distinction is not absolute and coupling between inter- and intramolecular modes is possible. 

In the examples smdied so far, the photoinduced short-time dynamics of a molecular system has been governed by a few high-frequency intramolecular vibrational modes that strongly couple to the electronic transition, a situation that... 

Even in a molecule the size of benzene the resolution achieved in this way is sufficient to investigate the dynamic behavior of individual rotational states. For this it is necessary to eliminate the Doppler broadening of the rovibronic transitions. Two methods have been applied (i) the elimination of Doppler broadening in a Doppler-free two-photon-transition and (ii) the reduction of Doppler broadening in a molecular beam. Measurements of the dynamic behavior have been performed in the frequency [3] and time domain [4]. We will briefly summarize the results from high-resolution measurements and discuss the conclusions on the intramolecular decay mechanism. Then it will be discussed how the intramolecular dynamics is influenced by the attachment of an Ar or Kr atom to the benzene molecule, leading to a weakly bound van der Waals complex. 

We have presented a new technique for the investigation of intramolecular couplings in the electronic ground state 50. The new technique of CIS is based on the special population dynamics induced by the coherent excitation of a three-level system with two narrow-band Fourier-transform-limited laser pulses. It allows the investigation of high-lying intermolecular vibrational states in the electronic ground state of van der Waals complexes. These... 

In conclusion in this work we have presented basic information on the nature of the coupling processes leading to the intramolecular dynamics in isolated molecules. This information is useful for the understanding of the origin and mechanism of the fast femtosecond energy flow in high valence and low Rydberg states. 

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