Theoretical study of the finite temperature spectroscopy in van der Waals clusters. III Solvated Chromophore as an effective diatomics

The absorption spectroscopy of calcium-doped argon clusters is described in terms of an effective diatomics molecule Ca-(Ar_n), in the framework of semiclassical vertical transitions. We show how, upon choosing a suitable reaction coordinate, the effective finite-temperature equilibrium properties can be obtained for the ground- and excited-surfaces from the potential of mean force (PMF). An extension of the recent multiple range random-walk method is used to calculate the PMF over continuous intervals of distances. The absorption spectra calculated using this single-coordinate description are found to be in good agreement with the spectra obtained from high-statistics Monte Carlo data, in various situations. For CaAr$_{13}$, we compare the performances of two different choices of the reaction coordinate. For CaAr_37, the method is seen to be accurate enough to distinguish between different low-energy structures. Finally, the idea of casting the initial many-body problem into a single degree of freedom problem is tested on the spectroscopy of calcium in bulk solid argon.Comment: 8 pages, 9 figure

Fear of Floating

In recent years, many countries have suffered severe financial crises, producing a staggering toll on their economies, particularly in emerging markets. One view blames fixed exchange rates-- soft pegs'--for these meltdowns. Adherents to that view advise countries to allow their currency to float. We analyze the behavior of exchange rates, reserves, the monetary aggregates, interest rates, and commodity prices across 154 exchange rate arrangements to assess whether official labels' provide an adequate representation of actual country practice. We find that, countries that say they allow their exchange rate to float mostly do not--there seems to be an epidemic case of fear of floating.' Since countries that are classified as having a free or a managed float mostly resemble noncredible pegs--the so-called demise of fixed exchange rates' is a myth--the fear of floating is pervasive, even among some of the developed countries. We present an analytical framework that helps to understand why there is fear of floating.

Fixing for Your Life

The Asian crisis took place against a background of exchange rate regimes that were characterized as soft pegs. This has led many analysts to conclude that the peg did it' and that emerging markets (EMs) should just say no' to pegged exchange rates. We present evidence that EMs are very different from developed economies in key dimensions that play a key role when it comes to the choice of exchange rate regime--floating for EMs is no panacea. In EMs currency crashes are contractionary, the adjustments in the current account are far more acute. Credibility and market access, as captured in the behavior of credit ratings and interest rates, is adversely affected by devaluations or depreciations. Exchange rate volatility is more damaging to trade and the passthrough from exchange rate swings to inflation is far higher in EMs. These differences between emerging and developed economies may explain EMs reluctance to tolerate large exchange rate movements. In a simple framework we illustrate why large exchange rate swings are feared when access to international credit may be lost.

Spatiotemporal instability of a confined capillary jet

Recent experimental studies on the instability appearance of capillary jets have revealed the capabilities of linear spatiotemporal instability analysis to predict the parametrical map where steady jetting or dripping takes place. In this work, we present an extensive analytical, numerical and experimental analysis of confined capillary jets extending previous studies. We propose an extended, accurate analytic model in the limit of low Reynolds flows, and introduce a numerical scheme to predict the system response when the liquid inertia is not negligible. Theoretical predictions show a remarkable accuracy with results from the extensive experimental exploration provided.Comment: Submitted to the Physical Review E (20-March-2008

Theoretical study of finite temperature spectroscopy in van der Waals clusters. II Time-dependent absorption spectra

Using approximate partition functions and a master equation approach, we investigate the statistical relaxation toward equilibrium in selected CaAr$_n$ clusters. The Gaussian theory of absorption (previous article) is employed to calculate the average photoabsorption intensity associated with the 4s^2-> 4s^14p^1 transition of calcium as a function of time during relaxation. In CaAr_6 and CaAr_10 simple relaxation is observed with a single time scale. CaAr_13 exhibits much slower dynamics and the relaxation occurs over two distinct time scales. CaAr_37 shows much slower relaxation with multiple transients, reminiscent of glassy behavior due to competition between different low-energy structures. We interpret these results in terms of the underlying potential energy surfaces for these clusters.Comment: 10 pages, 9 figure