On the chemical bonding effects in the Raman response: Benzenethiol adsorbed on silver clusters

We study the effects of chemical bonding on Raman scattering from benzenethiol chemisorbed on silver clusters using time-dependent density functional theory (TDDFT). Raman scattering cross sections are computed using a formalism that employs analytical derivatives of frequency-dependent electronic polarizabilities, which treats both off-resonant and resonant enhancement within the same scheme. In the off-resonant regime, Raman scattering into molecular vibrational modes is enhanced by one order of magnitude and shows pronounced dependence on the orientation and the local symmetry of the molecule. Additional strong enhancement of the order of $10^2$ arises from resonant transitions to mixed metal--molecular electronic states. The Raman enhancement is analyzed using Raman excitation profiles (REPs) for the range of excitation energies $1.6-3.0$ eV, in which isolated benzenethiol does not have electronic transitions. The computed vibrational frequency shifts and relative Raman scattering cross sections of the metal--molecular complexes are in good agreement with experimental data on surface enhanced Raman scattering (SERS) for benzenethiol adsorbed on silver surfaces. Characterization and understanding of these effects, associated with chemical enhancement mechanism, may be used to improve the detection sensitivity in molecular Raman scattering.Comment: 25 pages, 14 figures. Phys. Chem. Chem. Phys. in pres

Parameterized verification of transactional memories

We describe an automatic verification method to check whether transactional memories ensure strict serializability—a key property assumed of the transactional interface. Our main contribution is a technique for effectively verifying parameterized systems. The technique merges ideas from parameterized hardware and proto-col verification—verification by invisible invariants and symmetry reduction—with ideas from software verification—template-based invariant generation and satisfiability checking for quantified for-mulæ (modulo theories). The combination enables us to precisely model and analyze unbounded systems while taming state explosion. Our technique enables automated proofs that two-phase locking (TPL), dynamic software transactional memory (DSTM), and trans-actional locking II (TL2) systems ensure strict serializability. The verification is challenging since the systems are unbounded in sev-eral dimensions: the number and length of concurrently executing transactions, and the size of the shared memory they access, have no finite limit. In contrast, state-of-the-art software model checking tools such as BLAST and TVLA are unable to validate either system, due to inherent expressiveness limitations or state explosion

Resolution Enhancement of Thermal and Optical Nanolithography Using an Organic Dry Developing Resist and an Optimized Tip

Ultrahigh nanolithography resolution of 31 nm was achieved using thin film layers of naphthoquinones compounds. Dry nanolithography processes, negative and positive were developed, utilizing the thermal and optical properties of these compounds, by using an Atomic Force Microscope with a tapered optical tip. Negative nanolithography was achieved using a specially designed optical fiber tip transmitting 488 nm of light that functions as a near field optical source. Positive nanolithography was achieved by coating the fiber tip with a metal film to serve as a nano-heating source. Sub-wavelength gratings with a variable line width, fabricated using these processes, are demonstrated

Shape-Value Abstraction for Verifying Linearizability

Abstract. This paper presents a novel abstraction for heap-allocated data structures that keeps track of both their shape and their contents. By combining this abstraction with thread-local analysis and relyguarantee reasoning, we can verify a collection of fine-grained blocking and non-blocking concurrent algorithms for an arbitrary (unbounded) number of threads. We prove that these algorithms are linearizable, namely equivalent (modulo termination) to their sequential counterparts.

RGSep Action Inference

Abstract. We present an automatic verification procedure based on RGSep that is suitable for reasoning about fine-grained concurrent heapmanipulating programs. The procedure computes a set of RGSep actions overapproximating the interference that each thread causes to its concurrent environment. These inferred actions allow us to verify safety, liveness, and functional correctness properties of a collection of practical concurrent algorithms from the literature.

Model checking linearizability via refinement

10.1007/978-3-642-05089-3_21Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)5850 LNCS321-33