This thesis demonstrates the continued growth of single-walled carbon nanotubes (SWNTs) from seeded SWNTs in a way analogous to epitaxy or cloning; that is, the SWNTs grow as a seamless extension to the existing seeded SWNTs and have the same diameter and chirality as those of the SWNT seeds. The experiments were carried out in three key steps, including: (1) preparing a macroscopic array of open-ended SWNTs; (2) reductively docking transition metals as a catalyst to the nanometer-sized open ends; and then (3) heating the whole up to 700--850°C in the presence of a carbon feedstock such as ethanol or ethylene. The resulting SWNT ropes inherit the diameters and chirality from the seeded SWNTs, as indicated by the closely matched frequencies of Raman radial breathing modes before and after the growth. As a control, only sparse nanotubes grew from closed-ended SWNTs, ruling out spontaneous nucleation as a dominating mechanism in our experiments. This experiment proved for the first time the growth of SWNTs can be separated from the nucleation step. The ability to separate the typically inefficient nucleation step from the growth of SWNTs and to restart the growth opens the possibility of amplifying SWNTs with only the desired (n, m). The success in the continued growth was enabled with the creation of macroscopic arrays of open-ended SWNTs from a neat SWNT fiber. A variety of techniques including cryo-microtoming and surface etching chemistry have been developed to produce a macroscopic (∼1200mum2), aligned, and clean---largely free of amorphous carbon, oxides, and metal residuals---SWNT substrate with open-ended SWNTs aligned along the fiber axis. Alternatively, the fiber was milled perpendicular to the fiber axis with a gallium focused ion beam to produce a planar, free-standing, ultra-thin, "bed-of-nails" SWNT membrane---a single layer of parallel SWNTs densely packed and aligned along the normal of the membrane.

This thesis is concerned with non-adiabatic effects in alkali/halogen collision systems. After a general survey of non-adiabatic molecular collision theory, and its application to such systems, calculations have been performed relating to three topics : (i) Vibrational energy distributions resulting from electron transfer collisions between alkali metal atoms and halogen molecules are often treated by the multi-curve crossing approach to the classical path approximation, in the form of two approximations, one valid at high collision energy, the other at low energy; the performance of these is evaluated over a wide energy range by comparison with the results from an "exact" multi-curve crossing approach. (ii) Classical trajectory calculations for reactive alkali / halogen collisions are performed using a simple ionic potential energy surface, developed earlier to model the weakening of the halogen bond by the metal ion immediately after the electron transfer. Detailed comparison is made between the results and those from experiment; good agreement is obtained for K/I₂ and comparison of the results for K/I₂ and Cs/I₂ indicates that this effect is not merely dependent on the charge of the ion. (iii) The population of ground and excited sodium atoms resulting from Na/I charge neutralisation collisions is investigated using the multi-curve crossing approach. Although it has been suggested that population inversions may be produced by such a process, it is shown that this is only possible at extremely high collision energies.

The generalized local-spin-density functional (G-LSD) theory is proposed which avoids (a) the physical restriction used in the generalized exchange local-spin-density functional (GX-LSD) theory; (b) the homogeneous electron-density approximation in the Hartree-Fock-Slater (HFS) theory and in the Gaspar-Kohn-Sham (GKS) theory; and (c) the time-consuming step to search the optimal exchange parameter for each atom or ion in the X$ alpha$ and $ Xi$a theories. Theoretically, the G-LSD theory is more rigorous than the GX-LSD, HFS, GKS, and $ Xi$a theories. Numerically, the statistical total energies for atoms are better in the G-LSD theory than in the GKS theory. / Ionization potentials and electron affinities of atoms, the stability of singly and doubly charged negative ions, and the electronegativities, and hardnesses of the fractional charged atoms with Z $<$ 37 are calculated by the SIC-GX-LSD theory with the GWB Fermi-hole parameters and electron-correlation correction. / The self-interaction correction (SIC) is introduced into the multiple-Scattering X$ alpha$ (MS-X$ alpha$) method and used to calculate some molecules and molecular anions. The results show that the ionization potentials from the negative of the one-electron eigenvalues are as good as those obtained in the transition state calculation and in very good agreement with experiment.

Thesis (Ph.D.)--Lehigh University, 2007. / Adviser: Ivan Biaggio.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7403. Adviser: Klaus Schulten. Includes bibliographical references (leaves 72-79) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 7098. Adviser: Narayana R. Aluru. Includes bibliographical references (leaves 130-140) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--Lehigh University, 2010. / Adviser: Yujie J. Ding.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 6879. Adviser: Enrico Gratton. Includes bibliographical references (leaves 90-93) Available on microfilm from Pro Quest Information and Learning.

This thesis describes experimental work done with two of the smallest diatomic alkali molecules, 6Li2 and 23Na6Li, each formed out of its constituent atoms at ultracold temperatures. The 23Na6Li molecule was formed for the first time at ultracold temperatures, after previous attempts failed due to an incorrect assignment of Feshbach resonances in the 6Li+23Na system. The experiment represents successful molecule formation around the most difficult Feshbach resonance ever used, and opens up the possibility of transferring NaLi to its spin-triplet ground state, which has both magnetic and electric dipole moments and is expected to be long-lived. For 6Li2, the experimental efforts in this thesis have solved a long-standing puzzle of apparently long lifetimes of closed-channel fermion pairs around a narrow Feshbach resonance, finding that the lifetime is in fact short, as expected in the absence of Pauli suppression of collisions. Moreover, measurements of collisions of Li2 with free Li atoms demonstrates a striking first example of collisions involving molecules at ultracold temperatures described by physics beyond universal long-range van der Waals interactions.

Diatomic molecules are considered good candidates for the study of strongly correlated systems and precision measurement searches due to their combination of complex internal states and strong long-range interactions. Cooling molecules down to ultracold temperatures is often a necessary step for fully utilizing the power of the molecule. This requires a trap for molecules and the ability to cool molecules to the mK regime and below. A magneto-optical trap (MOT) is a good tool for achieving mK temperatures. However, extra care is needed for molecules to form the necessary quasi-closed cycling transitions due to molecule's complicated energy structure. In our work with CaF, we use two repump lasers to block vibrational leakage and selection rules for the rotational degree of freedom to achieve about 10^{5} photon cycles. The two-stage buffer gas beam source is a general method to generate a cold and slow beam of molecules with a forward velocity of about 50 m/s. The compatibility of the buffer-gas source with a MOT is studied and we confirm that such beams can be nicely compatible with MOTs using various atomic species. In order to load molecules into a MOT from even such a slow beam, additional slowing is required due to the low capture velocity of a molecular MOT (< 10 m/s). We apply a frequency-broadened “white-light” slowing on CaF from a two-stage source, demonstrating slowing of CaF below 10 m/s. An AC MOT, which provides active remixing of dark substates, is also developed and Li atoms are slowed and trapped. These are crucial ingredients for co-trapping CaF molecules and Li atoms and study their collisional properties, which would lead to sympathetic cooling of molecules down to ultracold temperatures. The achievement of slowing and development of this system allowed for the detailed study of the CaF laser cooling system, as well as physical processes involved with AC MOTs and the proposed MOT for CaF. Crucial knowledge of this archetypal system provides significant progress toward manipulation and control of molecules similar to what has been achieved with atoms and what is necessary for searches for new physics with ultracold molecules. / Physics