Direct observation of molecular structure by Coulomb explosion imaging

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To establish the technique "Coulomb explosion imaging (CE1)", collision experiments of highly charged ions with various molecules were carried out. Dissociation of the multiply charged molecular ion was induced by the collision of Ar highly ionized beam extracted from an ECR ion source, and the trajectories of the fragments were derived from the values of the positions and the time-of-flights. The main results are as follows.1 : CEI was done by the detection of all fragments of linear triatomic molecules, CO_2 and CS_2, and nonlinear triatomic molecule, NO_2. The results were consistent with the known bond angles. The velocity vectors of the dissociating fragments were analyzed in detail by the change of charge and the collision energy. It was clarified that the charge states of the target molecule are the most critical factor governing dissociation process.2 : By GEI based oh the C-D-D triple coincidence measurement (detection of part of the fragments) of CD_4, it was shown that D-C-D bond angle was rightly obtained. This result indicates the possibility of the local structure analysis by CEI.3 : The chirality of CD_4, which was distorted by the zero point vibrations, was analyzed demonstrating that the CEI method can distinguish the molecular chirality directly.4 : The new position sensitive detector, which combined the resistance substrate with the backgammon type electrode, was developed. The performance was evaluated, and it was shown that very high position and time resolution were obtained.The above results were announced in the scientific journals as papers, as well as in domestic and foreign conferences. And, the test equipment for collision experiments of fullerenes with highly charged ions was manufactured in order to analyze the dissociation process of the fullerenes from the new standpoint, and the preliminary time-of-flight analysis experiment of the product was carried out.