Semiclassical quantization of multidimensional systems

Low order classical perturbation theory is used to obtain semiclassical eigenvalues for a system of three anharmonically coupled oscillators. The results in the low energy region studied here agree well with the "exact" quantum values. The latter had been calculated by matrix diagonalization using a large basis set

Introduction: Climate Change and Planned Retreat

Chapter 1. This edited volume advances our understanding of climate relocation (or planned retreat), an emerging topic in the fields of climate adaptation and hazard risk, and provides a platform for alternative voices and views on the subject. As the effects of climate change become more severe and widespread, there is a growing conversation about when, where and how people will move. Climate relocation is a controversial adaptation strategy, yet the process can also offer opportunity and hope. This collection grapples with the environmental and social justice dimensions from multiple perspectives, with cases drawn from Africa, Asia, Australia, Oceania, South America, and North America. The contributions throughout present unique perspectives, including community organizations, adaptation practitioners, geographers, lawyers, and landscape architects, reflecting on the potential harms and opportunities of climate-induced relocation. Works of art, photos, and quotes from flood survivors are also included, placed between sections to remind the reader of the human element in the adaptation debate. Blending art – photography, poetry, sculpture – with practical reflections and scholarly analyses, this volume provides new insights on a debate that touches us all: how we will live in the future and where? Challenging readers’ pre-conceptions about planned retreat by juxtaposing different disciplines, lenses and media, this book will be of great interest to students and scholars of climate change, environmental migration and displacement, and environmental justice and equity

A simple classical model of infrared multiphoton dissociation

The classical mechanics of a system of two nonlinearly coupled oscillators driven by an oscillating electric field is studied. The presence of quasiperiodic and chaotic motion in the unforced system is shown to influence the nature of energy absorption. Two essentially different types of behavior are observed. In the first, energy is exchanged in a multiply periodic manner between the system and the forcing field. In the second regime, the energy exchange is erratic and a statistical analysis of a family of trajectories shows the role of the chaotic motion in the unforced system in the dissociation process. A theory for rate of photodissociation is presented and results are compared with those obtained from an ensemble of exact classical trajectories

A model for orientation effects in electron‐transfer reactions

A method for solving the single‐particle Schrödinger equation with an oblate spheroidal potential of finite depth is presented. The wave functions are then used to calculate the matrix element T_BA which appears in theories of nonadiabatic electron transfer. The results illustrate the effects of mutual orientation and separation of the two centers on TBA. Trends in these results are discussed in terms of geometrical and nodal structure effects. Analytical expressions related to T_BA for states of spherical wells are presented and used to analyze the nodal structure effects for T_BA for the spheroidal wells

Probing impulsive strain propagation with x-ray pulses

Pump-probe time-resolved x-ray diffraction of allowed and nearly forbidden reflections in InSb is used to follow the propagation of a coherent acoustic pulse generated by ultrafast laser-excitation. The surface and bulk components of the strain could be simultaneously measured due to the large x-ray penetration depth. Comparison of the experimental data with dynamical diffraction simulations suggests that the conventional model for impulsively generated strain underestimates the partitioning of energy into coherent modes.Comment: 4 pages, 2 figures, LaTeX, eps. Accepted for publication in Phys. Rev. Lett. http://prl.aps.or

Ultrafast changes in lattice symmetry probed by coherent phonons

The electronic and structural properties of a material are strongly determined by its symmetry. Changing the symmetry via a photoinduced phase transition offers new ways to manipulate material properties on ultrafast timescales. However, in order to identify when and how fast these phase transitions occur, methods that can probe the symmetry change in the time domain are required. We show that a time-dependent change in the coherent phonon spectrum can probe a change in symmetry of the lattice potential, thus providing an all-optical probe of structural transitions. We examine the photoinduced structural phase transition in VO2 and show that, above the phase transition threshold, photoexcitation completely changes the lattice potential on an ultrafast timescale. The loss of the equilibrium-phase phonon modes occurs promptly, indicating a non-thermal pathway for the photoinduced phase transition, where a strong perturbation to the lattice potential changes its symmetry before ionic rearrangement has occurred.Comment: 14 pages 4 figure

Fiber laser front end for high energy petawatt laser systems

We are developing a fiber laser front end suitable for high energy petawatt laser systems on large glass lasers such as NIF. The front end includes generation of the pulses in a fiber mode-locked oscillator, amplification and pulse cleaning, stretching of the pulses to >3ns, dispersion trimming, timing, fiber transport of the pulses to the main laser bay and amplification of the pulses to an injection energy of 150 {micro}J. We will discuss current status of our work including data from packaged components. Design detail such as how the system addresses pulse contrast, dispersion trimming and pulse width adjustment and impact of B-integral on the pulse amplification will be discussed. A schematic of the fiber laser system we are constructing is shown in figure 1 below. A 40MHz packaged mode-locked fiber oscillator produces {approx}1nJ pulses which are phase locked to a 10MHz reference clock. These pulses are down selected to 100kHz and then amplified while still compressed. The amplified compressed pulses are sent through a non-linear polarization rotation based pulse cleaner to remove background amplified spontaneous emission (ASE). The pulses are then stretched by a chirped fiber Bragg grating (CFBG) and then sent through a splitter. The splitter splits the signal into two beams. (From this point we follow only one beam as the other follows an identical path.) The pulses are sent through a pulse tweaker that trims dispersion imbalances between the final large optics compressor and the CFBG. The pulse tweaker also permits the dispersion of the system to be adjusted for the purpose of controlling the final pulse width. Fine scale timing between the two beam lines can also be adjusted in the tweaker. A large mode area photonic crystal single polarization fiber is used to transport the pulses from the master oscillator room to the main laser bay. The pulses are then amplified a two stage fiber amplifier to 150mJ. These pulses are then launched into the main amplifier chain. We are currently constructing a packaged prototype of this system, which will ultimately be deployed on the National Ignition Facility (NIF). In our talk we will discuss the packaged components as well as the numerous technical challenges that needed to be overcome in order to make this system possible. Of particular interest was the quality of recompressed pulses that could be achieved with a CFBG. We will show background free auto-correlation data from pulses with a dynamic range noise limited to six orders of magnitude that were stretched with a CFBG and then recompressed in a standard compressor (figure 2). We will also discuss in detail the impact of B-integral accumulation on the recompressed pulses. Our current system is projected to run at an accumulated B-integral of 7. However, because our injected system bandwidth is much wider than the NIF system bandwidth our system can tolerate this high B-integral

Compton Scattering Sources and Applications at LLNL

Abstract not provide