Near Resonance vibronic coupling. Isoquinoline

The interaction spectrum is considered resulting from the near-resonance coupling of a small number of vibronic levels of two different electronic states. In the simple model proposed, the interactions between the near-resonance states are first explicitly considered and then the off-resonance interactions are treated by perturbation theory. The model is applied to the isoquinoline spectrum and it is shown that for isoquinoline the latter interactions may be safely ignored. Good agreement is achieved between the theoretical and experimental spectra, and many puzzling features, such as the irregular nature of the sequence structure and the ambiguous isotope effects are readily explained. The lowest excited singlet state is the nπ*, and it is located within about 1000 cm^?1 of the first excited ¹ππ*. Two vibronic levels of the ¹nπ* state, corresponding to single quanta of the out-of-plane vibrations, are in near-resonance with the vibrationless ¹ππ* level.     

Rayleigh-Brillouin scattering in chalcogenide glasses of the Ge-As-S system

Rayleigh-Brillouin scattering in chalcogenide glasses of the Ge-As-S system was investigated for the (As₂S₃)_100?x (GeS₂)_x (x=0–100) series. The longitudinal hypersonic velocities, adiabatic elasto-optical constants (p ₁₂)_ad at frequencies of about 15 GHz, and Landau–Placzek ratios (R _LP) were determined.     

Pattern Matching with Swaps

Let a text string T of n symbols and a pattern string P of m symbols from alphabet Σ be given. A swapped version T′ of T is a length n string derived from T by a series of local swaps (i.e., t′_ℓ ← t_ℓ + 1 and t′_ℓ + 1 ← t_ℓ), where each element can participate in no more than one swap. The pattern matching with swaps problem is that of finding all locations i for which there exists a swapped version T′ of T with an exact matching of P in location i of T′. It has been an open problem whether swapped matching can be done in less than O(nm) time. In this paper we show the first algorithm that solves the pattern matching with swaps problem in time o(nm). We present an algorithm whose time complexity is O(nm^1/3 log m log σ) for a general alphabet Σ, where σ = min(m,Σ).     

Ab initio study of spectroscopic properties of the calcium hydride molecular ion

In the present work, all adiabatic potential energy curves, spectroscopic constants and dipole moments of CaH⁺ molecular ion dissociating below the ionic limit Ca²⁺H⁻ are presented. These curves are determined by an ab initio approach involving a non-empirical pseudo-potential for the Ca core, core-valence correlation accounted in operator form with two types of core polarization potentials (CPP) and full valence Configuration Interaction. The molecule is thus treated as a two-electron system. The potential energy curves and the spectroscopic constants are presented. In addition, the permanent and transition dipole moments are calculated for most of the states and reveal the underlying ionic states. A rather good agreement with the available theoretical works in the literature is obtained for the spectroscopic constants of the lowest states of the CaH⁺ molecule.     

Electronic spectra of azanaphthalenes: Mixed crystal spectra of quinoxaline and quinoxaline-d6

The following spectra have been measured at 4 K, in three polarizations: ${}^1\text{B}{}_1\text{(n,π}{}^1\text{) ←}{}^1\text{A}{}_1$ absorption of quinoxaline in durene, durene-d₁₄, naphthalene and naphthalene-d₁₀, and of quinoxaline-d₆ in durene and naphthalene. The polarized phosphorescence of quinoxaline-d₆ in durene is also recorded.The analyses permit unusually extensive assignments of excited state vibrational frequencies. Also noted are various crystal effects: isotope shifts, modification of molecular frequencies, prominence of Herzberg-Teller origins, site splittings, effects of perdeuterated hosts, and polarization ratios. An unusual line-splitting seen in durene is analyzed as a resonance between coincident a₁ and b₁ vibrations of the quinoxaline molecule, coupled through the exciton bands of the host.     

Detecting coherent patterns in a flume by using PIV and IR imaging techniques

We investigated the flow field in a turbulent boundary layer in a flume, by using Particle Image Velocimetry (PIV) and Hot-Foil Infrared Imaging (HFIRI) techniques. Coherent patterns in the flow were identified and characterized by using instantaneous velocity and temperature fields. The velocity fields in the streamwise–spanwise plane were measured in parallel to the temperature distribution of the flume bottom. The identified patterns are represented by means of their spatial characteristics – a non-dimensional spatial separation between streamwise patterns, ⁺.