PALNITKAR, SANJAY S.

English

Open Access Repository of Indian Theses

AbstractThis thesis reports the theoretical and experimental studies carried out to study the dissociation dynamics of multiply charged diatomic molecules (N2q+ and COq+) to gain insight into the electronic states of these molecular ions. On the theoretical front, ab initio calculations of potential energy curves for multiply charged N2q+ and COq+ (3≤q≤6) were performed to discuss the dissociation possibilities of these ions. Experimentally multiply charged N2 and CO molecular ions were generated in interaction of neutral parents with highly charged low energy Argon projectiles. The technique of time-of-flight mass spectrometry was used to study the interaction. The experimental data was obtained using time and position sensitive detectors in multi-hit coincidence mode. Kinetic energy release distributions were obtained for all the observed dissociation channels and were correlated to the existing and calculated potential energy curves of N2q+ and COq+ ions. In addition, this thesis reports the design and implementation of an electrostatic deceleration lens which would be used to decelerate and focus a beam of HCI having energy of few tens of keV/q so as to obtain a low energy (few tens of eV/q) well focused beam on the target. This setup is developed for carrying out ion-matter interaction studies with highly charged ions at much lower energies (~10 eV/q) and will be used to shed light on the role of the projectile's potential energy in ion-molecule interactions. With the new setup the ion-atom, ion-molecule interaction times will be of the order of few tens of femtoseconds. With these interaction times the initial as well the final states of the target atom or molecule are expected to be modified by the presence of the projectile. Quasi two body effects may appear in ion-atom interactions with the projectile and the atom being the two bodies, while ion-molecule collisions will offer a simple many body problem. A time-of-flight system using position sensitive detectors in multi-hit coincidence mode, coupled with the new setup will help us identify how the projectile modifies the states of the target. The multiple ionization and fragmentation of N2 induced by ion impact is studied using time and position sensitive detectors in multihit coincidence mode. With Ar9+ at a projectile velocity of 1 a.u. we observe a total of seven fragmentation channels originating from multiply charged transient molecular ions. The preference of symmetric charge breakup channels over the asymmetric ones is clearly observed. A signature of core excitation of the target followed by Auger emission in the N3+ - N3+ fragmentation channel. The kinetic energy release spectra of all the observed fragmentation pathways is explained on the basis of calculated ab initio (using multiconfiguration self-consistent-field method) potential energy curves. Ion-induced molecular fragmentation of CO has been studied using time-of-flight mass spectroscopy with position sensitive detectors in multihit coincidence mode. Ar8+ ions having a velocity of 1.1 a.u. were used as projectiles. The features observed in the kinetic energy release (KER) spectra for all the detected fragmentation channels are discussed in light of the existing and calculated ab initio potential energy curves. The preference of the symmetric breakup over the asymmetric one is clearly observed. For fragmentation channels originating from the same parent molecular ion, it is observed that the most probable KER value is higher for the dissociation channel having a higher charge on the oxygen ion. Occurrence for sharp peaks in KER spectra of some of the fragmentation channels hints towards the existence of shallow (possibly metastable) excited states of COq+ (q=4,5) molecular ions and calls for further theoretical investigations. 

MICROBIOLOGY AND BIOCHEMISTRY OF D-XYLOSE FERMENTATION

http://eprints.csirexplorations.com/190/1/Abstract.doc

MICROBIOLOGY AND BIOCHEMISTRY OF D-XYLOSE FERMENTATION

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