Statistical Spectroscopy of Quantum Chaos State in Vibrationally Highly Excited polyatomic Molecules

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This project aims at cooperative experimental and theoretical studies on intramolecular vibrational dynamics of highly excited polyatomic molecules which have been carried out in four laboratories of Tokyo, Cambridge, Grenoble and Paris.1. Vibrational dynamics of highly excited acetylene(1) MIT group proposed a chaotic vibrational dynamics by means of a statistical analysis of level energies of vibrationally highly excited acetylene.(2) Grenoble group claimed an incomplete chaotic dynamics of excited acetylene based on the Fourier analysis of the spectral data obtained by MIT group.(3) Tokyo group observed a dispersed fluorescence spectrum of acetylene in a single rovibronic level to obtain a global feature of the vibrational level structure. They could analyze it in terms of an anharmonic expansion function assuming five normal modes in an energy region up to around 14, 000 cm^<-1>. Beyond this energy, two CH bending, modes (trans and cis) couple each other, so that a local chaotic dy … More namics is realized within these modes. Couplings to other modes occur in another stage approaching a final full chaotic dynamics.(4) Following the above proposal, MIT group confirmed an anharmonic coupling scheme between two CH stretching modes based on the high-resolution SEP spectrum of acetylene.2. Unimolecular dissociation reaction of NO_2(1) Tokyo group succeeded to take a state-selected photofragment (O or NO) excitation spectrum of NO_2. The observed spectrum showed a line structure which indicated the dissociation reaction via highly excited vibrational states of N0_2.(2) The vibrational level structure of excited N0_2 was discussed by Grenoble group, who predicted a chaotic level structure even in the region below the dissociation threshold.3. Structure and dynamics of electronically excited van der Waals complexes(1) Tokyo group predicted the structure of HgAr_2 complex by means of LIF spectroscopy and optical-optical double resonance method.(2) Orsay group discussed the structure of HgAr_2 based on a semi-empirical calculation of the potential surface as well as resonantly enhanced multiple photon ionization method. Less