Advances in Chemical Physics is the only series of volumes available to represent the cutting edge of research in the discipline. It creates a forum for critical, authoritative evaluations of advances in every area of the chemical physics field. Volume 128 continues to report recent developments with significant, up-to-date chapters by internationally recognized researchers. Volume 128 includes: "Nucleation in Polymer Crystallization," by M. Muthukumar; "Theory of Constrained Brownian Motion," by David C. Morse; "Superparamagnetism and Spin-glass Dynamics of Interacting Magnetic Nanoparticle Systems," by Petra E. Jönnson; "Wavepacket Theory of Photodissociation and Reactive Scattering," by Gabriel G. Balint-Kurti; and "The Momentum Density Perspective of the Electronic Structure of Atoms and Molecules," by Ajit J. Thakkar. Students and professionals in chemical physics and physical chemistry, as well as those working in the chemical, pharmaceutical, and polymer industries, will find Advances in Chemical Physics, Volume 128 to be an indispensable survey of the field.