Observed Intensity Distribution Research Articles

The Comet-Tail (A2Πi–X2Σ+) System of 12C16O+: A Reinvestigation

The emission spectrum of the comet-tail (A2Πi–X2Σ+) system of 12C16O+ produced in the cathode glow of a hollow-cathode discharge tube and photographed in the spectral region 3345–8500 Å at high resolution was reinvestigated. Detailed rotational analysis of 10 bands involving 5 vibrational levels v = 0 to 4 of each of the A and X states was carried out. Spin-splitting of the rotational levels was observed for the analyzed bands. The observed intensity distribution of the branches is found to be in good agreement with theoretical calculations. Molecular constants for both the A and X states were obtained from a global fit of the present data of the A–X system and the infrared and microwave data available from the literature for v = 0, 1, 2, 3, and 4 of state X, using effective Hamiltonian for the A2Π state and matrix elements for both A and X states. The present work suggests that the A2Πi state changes from Hund's case (a) at low J values to Hund's case (b) at high J values.

The Major Gulf of the Aqaba Earthquake, 22 November 1995 – Maximum Intensity Distribution

The major earthquake of 22 November 1995, with a moment magnitude MW = 7.1 and a local magnitude ML 6.2, was the beginning of a seismic swarm that occurred in the central part of the Gulf of Aqaba. During this swarm, thousands of earthquakes occurred with local magnitude ranging between 2 and 6.2 from 22 November 1996 to 31 December 1997, when 2089 earthquakes were detected and/or analyzed by the Jordan Seismological Observatory (JSO). The major earthquake strongly affected the near shoreline cities (Figure 1). The maximum observed intensity on these cities was VIII on the modified Mercalli intensity (MMI) scale. A questionnaire was distributed in the main cities of Jordan one week after the major earthquake. The results of this investigation, which demonstrated the observed intensity distribution for Aqaba city, shows a relationship between local conditions, such as geological foundations and topographical characters, and the extent of the destruction. This conclusion was supported by the maximum peak ground acceleration (PGA) measurements inside Aqaba and Eilat cities. From the results of this questionnaire compiled inside Jordan, and other reports and readings compiled from other nearby countries outside Jordan, a preliminary regional iso-intensity map for this major earthquake of 22 November 1995 is presented in this study.

SCATTERING OF RADIO WAVES AND PROBABILITY DISTRIBUTION OF INTENSITY OF SOLAR NOISE STORMS

The radiation of solar noise storms (NS) traverses the same regions of the outer corona which are responsible for the scintillation of remote radio sources when eclipsed by the Sun. It is shown that the observed intensity distribution of NS (as a function of time) is compatible with the distribution of scattered signal. Therefore, there is an alternative explanation of the `burst' component of NS due to coronal scattering, without assuming an impulsive source.

The December 5th, 1456 Central Italy Earthquake: A Discussion of a Possible Reshaping of Intensity Distribution by Vectorial Modelling

—A study of the intensity distribution of the earthquake of December 5th 1456, which affected a large area of central and southern Italy was carried out, verifying, through a recently proposed methodology, the two hypotheses assumed by different authors for one single seismic event and three distinct and close ones. This methodology is based on a vectorial modelling of the macroseismic intensity distribution which aims at determining the epicentre and the principal (minimum and maximum) attenuation directions.¶The study was structured, considering each of the two assumed hypotheses, in a set of tests obtained for the macroseismic field and the intensity map, by analysing different configurations of the observed intensity distribution.¶The results obtained are in agreement with the hypothesis of the time coexistence of three distinct seismic events, for which the calculated epicentres and the principal attenuation directions are compatible with the observed intensity distribution and with the tectonic trend of the Apennine region, respectively.

The Gunn—Peterson effect and the Lyman alpha forest

We show that spatial correlations in a stochastic large-scale velocity field in an otherwise smooth intergalactic medium (homogeneous comoving density) superposed on the general Hubble flow may cause a ‘line-like’ structure in QSO spectra similar to the population of unsaturated Lyα forest lines which usually are attributed to individual clouds with 1011 ≲NHi 5 × 1013 cm−2. Therefore there is no clear observational distinction between a diffuse intergalactic medium and discrete intergalactic clouds. It follows that the H i density in the diffuse intergalactic medium might be substantially underestimated if it is determined from the observed intensity distribution near the apparent continuum in high-resolution spectra of QSOs. Our tentative estimate implies a diffuse neutral hydrogen opacity τGP ∼ 0.3 at z ∼ 3 and a current baryon density ΩIGM ≃ 0.08, assuming a Hubble constant H0 = 70 km s−1 Mpc−1.

Experimental and theoretical vibrational overtone spectra of vCH=3, 4, 5, and 6 in formaldehyde (H2CO)

We present the first photoacoustic absorption spectra of higher C–H stretching overtones in formaldehyde up to the visible spectral region. The analysis of the coarse rotational structure on the basis of asymmetric rotor simulations provides band centers up to the fifth overtone (vCH=6). A two dimensional normal coordinate model for the C–H stretching degrees of freedom explains the observed polyad structure of the spectrum using ab initio (MP2/6-311G**) potential energy and electric dipole functions. The observed intensity distribution reflects the increasing local mode character of higher overtone wave functions within the normal coordinate subspace.

REM study of high index Si(5 5 12) flat surfaces

We found high index Si(5 5 12) flat surfaces on an inner cylindrical surface made in a Si(110) wafer. Fringes of about 5 nm in spacing were seen on the (5 5 12) surface. Assuming a simple structure model of the (5 5 12) surface we calculated an intensity distribution in the RHEED pattern. The result coincided qualitatively with an observed intensity distribution. The (5 5 12) surface is inclined by about 5.3° from a (113) surface, and so-called hill and valley structures of the (5 5 12) and the (113) surfaces were observed at orientations between these two surfaces. It was found that surface morphology on the (5 5 12) surface changed depending on the heating current direction at about 1200°C. It was also found that a surface structural phase transition, considered to be a roughening transition, occurred at about 900°C.

The width of the gamma-ray burst luminosity function

We examine the width of the gamma-ray burst (GRB) luminosity function through the distribution of GRB peak count rates, C$_{\rm{peak}}$, as detected by BATSE (\cite{batse:93}). In the context of galactic corona spatial distribution models, we attempt to place constraints on the characteristic width of the luminosity function by comparing the observed intensity distribution with those produced by a range of density and luminosity functions. We find that the intrinsic width of the luminosity function cannot be very well restricted. However, the distribution of intrinsic luminosities of {\it detected bursts} can be limited: we find that most observed bursts have luminosities that are in a range of one to two decades, but a significant population of undetected less luminous bursts cannot be excluded. These findings demonstrate that the assumption that GRB are standard candles is sufficient but not necessary to explain the observed intensity distribution. We show that the main reason for the relatively poor constraints is the fact that the bright-end part of the GRB flux distribution is not yet sampled by BATSE, and better sampling in the future may lead to significantly stronger constraints on the width of the luminosity function.

Electron correlation in Xe 4d5/2-16p-->5p-26p resonant Auger transitions studied by utilizing the Auger resonant Raman effect.

The Auger resonant Raman effect provides a unique method to eliminate the lifetime broadening in resonant Auger spectra. The method is now used to resolve experimentally the fine structure of the Xe 4${\mathit{d}}_{5/2}^{\mathrm{\ensuremath{-}}1}$6p\ensuremath{\rightarrow}5${\mathit{p}}^{\mathrm{\ensuremath{-}}2}$6p transitions. The strength of the electron correlation effects has been studied by comparing the observed intensity distribution with multiconfiguration Dirac-Fock predictions.

Equatorial A-band and I-band X-ray Diffraction from Relaxed and Active Fish Muscle: Further Details of Myosin Crossbridge Behaviour

It has been known for many years that the vertebrate striated muscle A-bands and I-bands both contribute to the observed equatorial X-ray diffraction patterns. Despite this, the observed equatorial patterns, with the exception of the clearly distinct Z-reflection, have often been analysed as coming solely from the A-band, since it has not been possible to separate the observed intensity distribution into individual A-band and I-band contributions. Here we show, for the case of diffraction from the highly ordered muscles in bony fish, that it is possible to separate these contributions to the diffraction patterns from intact muscles and to compute separate electron density maps for the A and I-bands. Difference A-band density maps between resting and active muscles are distinctly altered when the I-band contribution is removed from the observed equatorial intensity. Results from resting and fully active fish muscle A-bands are compared and interpreted in terms of myosin crossbridge movements; the observations are consistent with specific crossbridge labelling of actin filaments, with a strong azimuthal component of crossbridge movement towards actin.From electron microscopy of freeze-substituted fish muscle, it is shown that the I-band X-ray diffraction pattern probably arises mainly from the thin filament arrangement immediately adjacent to the Z-band.

Semiclassical calculation of the probabilities for collision-induced vibrational transitions in Ar *2

Although the VUV continua emitted by rare gas excimers have been extensively investigated, no theoretical calculations are available for their intensity distribution. In this Letter a semiclassical method, based on the split operator technique, has been used to describe the collisions between Ar 2( 3Σ + u) excimers and ground state Ar atoms. The experimentally observed intensity distribution in the so-called first and second VUV continuum has been qualitatively reproduced. The calculations yield a value of ν=(4.10±0.27)×10 6 p (s −1) for the global vibrational relaxation process frequency, where p is the pressure in Torr.

A laser-induced fluorescence study of the BiF A O+→X1 O+ system in the region 6550 to 7400 Å: Rotational analysis and evidence for an A O+ state potential maximum

Eighteen previously unobserved bands belonging to the BiF A O+→X1 O+ system have been identified in the region between 6550 and 7400 Å. Nine bands representing v′=27–29 and v″=40–45 have been rotationally analyzed, and the v′=27 and v′=29 states exhibit strong homogeneous perturbations. These upper state levels are also observed to predissociate, providing evidence for an A O+ state potential maximum which has been theoretically predicted. A limiting curve of dissociation suggests a rotationless potential maximum at 32 674±822 cm−1. This energy must correspond to a potential maximum if it is to be reconciled with recent thermochemical measurements of the ground state dissociation energy, D00=3.76±0.13 eV. The new spectroscopic constants have been included in a calculation of Rydberg–Klein–Rees potential curves for both states. Franck–Condon factors calculated from these potentials are qualitatively consistent with the observed intensity distribution. Measured collision free radiative lifetimes are consistent with known A O+ state lifetimes for nonpredissociated states and are found to be shorter for predissociated states.

Directionally scattered optical second-harmonic generation with surface plasmons

The spatial distribution of scattered optical second-harmonic generation owing to prism-coupled surface plasmon excitation at a silver-quartz crystal interface is studied. This spatial pattern, which has the shape of a limited arc radiated in the direction normal to the interface, can geometrically be explained in terms of the beating between the forward incident and backward scattered surface plasmons. The observed intensity distribution of the scattered harmonic light cannot be fitted by a single-scattering theory; thus the dominant contribution to the scattering arises from multiply scattered surface plasmons that may be interpreted in terms of enhanced backscattering.

Infrared spectrum of t-butyl hydroperoxide excited to the 4νOH vibrational overtone level

The infrared predissociation spectrum of t-butyl hydroperoxide excited to the 4νOH level reveals extensive mixing between the zeroth-order OH stretch state and nearly isoenergetic zeroth-order dark states. Because most of these dark states have an OH stretch quantum number of zero, the predissociation spectrum strongly resembles the infrared spectrum of an unexcited molecule. The observed intensity distribution in the predissociation spectrum is what one would expect if the eigenstates prepared by 4νOH vibrational overtone excitation were statistical mixtures of all the nearly isoenergetic zeroth-order states.

The A′2Δ-X2Σ+ transition in BaH

Of the twelve possible branches in the 0-0 bands of the forbidden systems A′2Δ-X2Σ+ of BaH and BaD, only three are found to be strong [1], namely R12, Q12 and Q21. These systems become allowed by mixing of the 2Δ state with both the nearby states A2Π and B2Σ+, and interference between transition moments leads to loss of intensity in many branches and to reinforcement in the branches observed to be strong. Semiquantitative agreement with the observed intensity distribution in BaH is obtained if μ‖ is taken to be between -μ⊥ and -2μ⊥.

Twinning effects in the orthorhombic form of a Ba 2YCu 3O 7− x superconductor

Twinning effects in a Ba 2YCu 3O 7− x superconductor (orthorhombic form) have been analyzed by X-ray diffraction techniques. Regions of reciprocal space surrounding the (220), the (2 20) , the (400), and the (040) reflections for each of three twinned crystals were mapped on a single crystal diffractometer. Various modes of twinning were modeled by computer and the results were compared to the observed intensity distribution in the proximity of these reflections. A twinning mode based on a main and a smaller satellite crystal, each contining a mirror along h h0 , with the satellite crystal rotated 90° relative to the main crystal gave the best agreement to the observed data.

Optical and infrared surface photometry of NGC 3077

NGC 3077, a small Irr II galaxy, is linked to its neighbor M81 by an H I bridge, which was formed by a tidal interaction between the two galaxies. Photoelectric U, B, and V, photovoltaic K, and four filter CCD surface photometry of NGC 3077 was obtained using the Wyoming Infrared Observatory 2.3 m telescope and the Lowell Observatory 1.8 m telescope. Detailed examination of the data in all filters indicates that the optical position of the galaxy listed by Gallouet and Heidmann corresponds not to the physical center of the galaxy, but to a bright star cluster, unresolved in our data, which appears to be only 10-30 million years old. The mass, density, and optical depths of a prominent absorption region near the nucleus of NGC 3077 are determined and found to be similar to those of galactic dust clouds associated with star-formation sites. The observed intensity distribution at various wavelengths indicates that NGC 3077 was an elliptical galaxy before its interaction with M81. During the interaction, NGC 3077 acquired the interstellar material which is currently forming stars in its central regions.

Quantum-chemical analysis of the absorption and emission spectra of coronene

The vibronic, Franck—Condon and Duschinsky activity in the S 0–S 1 transition of coronene is investigated by quantum-chemical methods with the aim of clarifying the assignments and accounting for the observed intensity distribution.

Role of stacking faults in solid state transformations

This article illustrates the two different roles played by stacking faults in solid state transformations viz. (i) in accommodating part of the transformation strains as observed in the noble metal-based alloys undergoing martensitic transformations, and (ii) in providing a mechanism for changing the stacking sequence of layers in a variety of materials like SiC, ZnS, Co and its alloys, and certain steels. Diffraction patterns taken from the martensitic phases of noble-metal-based alloys as well as from SiC and ZnS crystals undergoing transformation from one close-packed modification to another reveal the presence of characteristic diffuse streaks. It is shown that from a theoretical analysis of the observed intensity distribution along streaked reciprocal lattice rows in terms of physically plausible models for the geometry and distribution of faults, one can make a choice between various possible routes for transformation. From simple computer simulation studies, it is shown that the observed arrest of transformations in SiC is essentially due to the insertion of stacking faults in a random space and time sequence leading to an irregular distribution of solitons.

Auger transitions in open-shell configurations withns (n=4,5,6)outer electron

Nonradiative transitions in nonclosed-shell atoms K ($Z=19$), Ag ($Z=47$), and Au ($Z=79$) with $\mathrm{ns} (n=4,5,6)$ outer electron are studied by comparing the calculated transition rates with the experimental ones. Auger transitions involving the next inner shell show clear fine structure due to the coupling of the outer $\mathrm{ns}$ electron with the holes producted in the Auger decay. The observed intensity distribution is found to be reproduced reasonably well with the calculations which explicitly take into account the open-shell structure.