X ray emission spectroscopy of bulk liquid water in no man s land

The structure of bulk liquid water was recently probed by x ray scattering below the temperature limit of homogeneous nucleation TH of amp; 8764;232 K [J. A. Sellberg et al., Nature 510, 381 384 2014 ]. Here, we utilize a similar approach to study the structure of bulk liquid water below TH using oxygen K edge x ray emission spectroscopy XES . Based on previous XES experiments [T. Tokushima et al., Chem. Phys. Lett. 460, 387 400 2008 ] at higher temperatures, we expected the ratio of the 1b1 amp; 8242; and 1b1 amp; 8242; amp; 8242; peaks associated with the lone pair orbital in water to change strongly upon deep supercooling as the coordination of the hydrogen H bonds becomes tetrahedral. In contrast, we observed only minor changes in the lone pair spectral region, challenging an interpretation in terms of two interconverting species. A number of alternative hypotheses to explain the results are put forward and discussed. Although the spectra can be explained by various contributions from these hypotheses, we here emphasize the interpretation that the line shape of each component changes dramatically when approaching lower temperatures, where, in particular, the peak assigned to the proposed disordered component would become more symmetrical as vibrational interference becomes more importan

Selective gating to vibrational modes through resonant X ray scattering

The dynamics of fragmentation and vibration of molecular systems with a large number of coupled degrees of freedom are key aspects for understanding chemical reactivity and properties. Here we present a resonant inelastic X ray scattering RIXS study to show how it is possible to break down such a complex multidimensional problem into elementary components. Local multimode nuclear wave packets created by X ray excitation to different core excited potential energy surfaces PESs will act as spatial gates to selectively probe the particular ground state vibrational modes and, hence, the PES along these modes. We demonstrate this principle by combining ultra high resolution RIXS measurements for gas phase water with state of the art simulation

One dimensional cuts through multidimensional potential energy surfaces by tunable x rays

The concept of the potential energy surface PES and directional reaction coordinates is the backbone of our description of chemical reaction mechanisms. Although the eigenenergies of the nuclear Hamiltonian uniquely link a PES to its spectrum, this information is in general experimentally inaccessible in large polyatomic systems. This is due to near degenerate rovibrational levels across the parameter space of all degrees of freedom, which effectively forms a pseudospectrum given by the centers of gravity of groups of close lying vibrational levels. We show here that resonant inelastic x ray scattering RIXS constitutes an ideal probe for revealing one dimensional cuts through the ground state PES of molecular systems, even far away from the equilibrium geometry, where the independent mode picture is broken. We strictly link the center of gravity of close lying vibrational peaks in RIXS to a pseudospectrum which is shown to coincide with the eigenvalues of an effective one dimensional Hamiltonian along the propagation coordinate of the core excited wave packet. This concept, combined with directional and site selectivity of the core excited states, allows us to experimentally extract cuts through the ground state PES along three complementary directions for the showcase H2O molecul

A study of the water molecule using frequency control over nuclear dynamics in resonant X ray scattering

In this combined theoretical and experimental study we report a full analysis of the resonant inelastic X ray scattering RIXS spectra of H 2O, D 2O and HDO. We demonstrate that electronically elastic RIXS has an inherent capability to map the potential energy surface and to perform vibrational analysis of the electronic ground state in multimode systems. We show that the control and selection of vibrational excitation can be performed by tuning the X ray frequency across core excited molecular bands and that this is clearly reflected in the RIXS spectra. Using high level ab initio electronic structure and quantum nuclear wave packet calculations together with high resolution RIXS measurements, we discuss in detail the mode coupling, mode localization and anharmonicity in the studied system

Ultrafast dissociation features in RIXS spectra of the water molecule

In this combined theoretical and experimental study we report on an analysis of the resonant inelastic X ray scattering RIXS spectra of gas phase water via the lowest dissociative core excited state 1s amp; 8722;1O4a11 amp; 12297;. We focus on the spectral feature near the dissociation limit of the electronic ground state. We show that the narrow atomic like peak consists of the overlapping contribution from the RIXS channels back to the ground state and to the first valence excited state 1b amp; 8722;114a11 amp; 12297; of the molecule. The spectral feature has signatures of ultrafast dissociation UFD in the core excited state, as we show by means of ab initio calculations and time dependent nuclear wave packet simulations. We show that the electronically elastic RIXS channel gives substantial contribution to the atomic like resonance due to the strong bond length dependence of the magnitude and orientation of the transition dipole moment. By studying the RIXS for an excitation energy scan over the core excited state resonance, we can understand and single out the molecular and atomic like contributions in the decay to the lowest valence excited state. Our study is complemented by a theoretical discussion of RIXS in the case of isotopically substituted water HDO and D2O where the nuclear dynamics is significantly affected by the heavier fragments mas

Compact Time and Determinism for Bosons: foundations

Free bosonic fields are investigated at a classical level by imposing their characteristic de Broglie periodicities as constraints. In analogy with finite temperature field theory and with extra-dimensional field theories, this compactification naturally leads to a quantized energy spectrum. As a consequence of the relation between periodicity and energy arising from the de Broglie relation, the compactification must be regarded as dynamical and local. The theory, whose fundamental set-up is presented in this paper, turns out to be consistent with special relativity and in particular respects causality. The non trivial classical dynamics of these periodic fields show remarkable overlaps with ordinary quantum field theory. This can be interpreted as a generalization of the AdS/CFT correspondence.Comment: For editorial reasons the present version (0903.3680v5 accepted for publication in Found. Phys.) is focused on the foundational points of 0903.3680v4 (par.1, par.2 and par.3.2). The remaining parts (par.3.1, app.A and app.B) will be extended and published in dedicated papers. 28 pages, 3 figure

Production Test Rig for the ATLAS Level-1 Calorimeter Trigger Digital Processors

The Level-1 Calorimeter Trigger is a digital pipelined system, reducing the 40 MHz bunch-crossing rate down to 75 kHz. It consists of a Preprocessor, a Cluster Processor (CP), and a Jet/Energy-sum Processor (JEP). The CP and JEP receive digitised trigger-tower data from the Preprocessor and produce electron/photon, tau, and jet trigger multiplicities, total and missing transverse energies, and Region-of-Interest (RoI) information. Data are read out to the data acquisition (DAQ) system to monitor the trigger by using readout driver modules (ROD). A dedicated backplane has been designed to cope with the demanding requirements of the CP and JEP sub-systems. A number of pre-production boards were manufactured in order to fully populate a crate and test the robustness of the design on a large scale. Dedicated test modules to emulate digitised calorimeter signals have been used. All modules, cables and backplanes on test are final versions for use at the LHC. This test rig represents up to one third of the Level-1 digital processor system. Real-time data between modules were processed and time-slice readout data was transferred to the ROD at a trigger rate up to 100 kHz. Intensive testing consisted of checking the readout data by comparing to hardware simulations of the trigger. Domains of validity of the boards were also measured and dedicated stressful data patterns were used to check the reliability of the system. Tests results have been successful and the Level-1 calorimeter trigger system is proceeding to full production

First Measurements with the ATLAS Level-1 Calorimeter Trigger PreProcessor System

The ATLAS level-1 calorimeter trigger is a hardware-based system with the goal of identifying high-pT objects within an overall latency of 2.5 μs. It is composed of a PreProcessor system which digitises 7200 analogue channels, determines the bunchcrossing of the interaction and provides a fine timing and energy calibration; and two subsequent digital processors. The PreProcessor plays a central role during integration of the system as it provides digitisation and readout of calorimeter signals and serves as a digital signal source for the subsequent processors. In this presentation the system architecture, the board production testing, and cable installation are described. Results on commissioning efforts and signal integrity tests are presented