Amarjit Sen

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


A storage ion source based on the principle of confinement of charged particles by inhomogeneous oscillatory electric fields has been built for the production of low vibrational state ions. Using a gas mixture of H(,2) and rare gases (Ne and He) in the source at high pressure, higher vibrational states of H(,2)('+) and H(,3)('+) ions have been effectively quenched by ion-molecule reactions and collisional deactivation. State-selected ion beams of 10('-9)A or more have been obtained.;A new low energy crossed beam apparatus has been constructed to determine the internal energy of the ions by threshold measurement of collisional dissociation with a He jet. With a H(,2) + Ne (1:5 ratio) mixture in the source at 80 mtorr, H(,2)('+) ions are found to be in v = 0 and 1 states only. The H(,3)('+) ions have also been examined by collisional dissociation and are found to be in their ground vibrational states.;The H(,2)('+) ions from a colutron ion source have also been examined under similar conditions for comparison. The threshold measurements indicate that vibrational levels as high as v = 9 may be present.;In addition, vibrationally deexcited ions from a rf discharge source using rare gas mixtures with H(,2) at high pressure have been used to remeasure the dissociative recombination cross sections of H(,2)('+) through the energy range 0.01 - 1.0 eV in the MEIBE apparatus. Our calculations show that H(,2)('+) ions in vibrational levels up to v = 5 may be present contrary to the earlier belief of Auerbach et al. that only levels up to v = 2 were present. The DR cross sections are found to obey an E('-0.87) power law dependence and the derived rate coefficients satisfy an electron temperature dependence of T(,e)('-0.4) in the range 10('2)K to 10('4)K. Evidence of some structure in the cross section versus energy curves has been reaffirmed.



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