Near-infrared laser spectroscopy of NiI

Laser-induced fluorescence spectrum of NiI in the near infrared region of 714-770 nm has been recorded. Seven bands belonging to three electronic transition systems were observed and analyzed: the (0,0), (1,0), and (2,0) bands of [13.3] (2)Sigma(+)-A (2)Pi(3/2) system; the (1,1) and (0,1) bands of [13.9] (2)Pi(3/2)-X (2)Delta(5/2) system; and the (0,0) and (1,0) bands of [13.9] (2)Pi(3/2)-A (2)Pi(3/2) system. Spectra of isotopic molecules confirmed the vibrational quantum number assignment of the observed bands. Least-squares fit of rotationally resolved transition lines yielded accurate molecular constants for the v=0-2 levels of the [13.3] (2)Sigma(+) state, the v=0 level of the A (2)Pi(3/2), and the v=1 level of the X (2)Delta(5/2) state. The vibrational separation, DeltaG(1/2), of the ground state was measured to be 276.674 cm(-1). With the observation of the [13.9] (2)Pi(3/2)-A (2)Pi(3/2) and [13.9] (2)Pi(3/2)-X (2)Delta(5/2) transitions, we accurately determined the energy separation between the A (2)Pi(3/2) and the X (2)Delta(5/2) to be 163.847 cm(-1). This confirms that the order of the A (2)Pi(3/2) and X (2)Delta(5/2) states in NiI is reversed when compared with other nickel monohalides.     

Laser spectroscopy of FeO: Rotational analysis of some subbands of the orange system

Extensive laser excitation spectra and rotationally resolved laser-induced fluorescence spectra have been recorded for the “orange system” of gaseous FeO in the wavelength regions 5790–6140 and 5580–5640 Å. Detailed rotational analyses have been performed for about $\text{20}\text{Ω}\text{′}$ substates lying between 16 350 and 18 550 cm^?1. These are found to comprise a very severely perturbed ⁵Δ_i excited electronic state with a bond length of about 1.69 Å (which is responsible for the parallel polarization of the electronic transition from the ⁵Δ_i ground electronic state) and a large number of “extra” $\text{Ω}$ substates with B′ values ranging from 0.38 to 0.50 cm^?1, which almost certainly belong to high vibrational levels of lower-lying electronic states. Evidence about the natures of the “extra” states is confusing, however, with the ⁵⁴FeO⁵⁶FeO isotope shifts apparently being in conflict with the patterns of vibrationally resolved laser-induced fluorescence. Every single $\text{Ω}$ substate that has been analyzed shows rotational perturbations of varying severity. The density and magnitude of the rotational perturbations are quite exceptional for a diatomic molecule, and result in a new type of totally chaotic diatomic spectrum. There is a remarkable similarity to the visible spectrum of NO₂: in NO₂ the complications arise from the high density of perturbing ground state vibrational levels; in FeO there is a correspondingly high density of perturbing electronic states at lower energy. The great complexity of the FeO spectrum arises because the states are in an awkward intermediate spin-coupling case which still resembles Hund's case (a) but shows strong tendencies toward Hund's case (c) coupling.     

Predissociated rotational structure in the 2490-Å band of 15NO2

The rotational structure of the 000-000 band of the 2490-Å system of ¹⁵NO₂ ($\text{2}{}^2\text{B}{}_2\text{-}\text{X}\text{?}{}^2\text{A}{}_1$) has been analyzed from high dispersion grating spectrograph plates. The band is found to be slightly predissociated, exactly as in the ¹⁴NO₂ isotope, which suggests that it might be usable for laser separation of the isotopes of nitrogen; tables of the wavenumbers of the lines are given. The upper-state molecular constants are close to the values calculated by the isotope relations from those of ¹⁴NO₂.     

Building Pb nanomesas with atomic-layer precision

We demonstrate a novel scheme for manipulating metallic nanostructures involving a macroscopic number of atoms, yet with precise control in their local structures. The scheme entails a two-step process: (a) a triggering step using a scanning tunneling microscope, followed by (b) self-driven and self-limiting mass-transfer process. By using this scheme, we construct Pb nanomesas on Si(111) substrates whose thickness can be controlled with atomic-layer precision. The kinetic barrier for the mass transfer and the underlying mechanism behind this novel manipulation are determined.     

On the inventory model with variable lead time and price–quantity discount

In this paper, we propose a mixed integer optimization approach for solving the inventory problem with variable lead time, crashing cost, and price–quantity discount. A linear programming relaxation based on piecewise linearization techniques is derived for the problem. It first converts non-linear terms into the sum of absolute terms, which are then linearized by goal programming techniques and linearization approaches. The proposed method can eliminate the complicated multiple-step solution process used in the traditional inventory models. In addition, the proposed model allows constraints to be added by the inventory decision-maker as deemed appropriate in real-world situations.     

Far-infrared laser magnetic resonance spectrum of34S16O in X3Σ− state

The far-infrared laser magnetic resonance spectrum of³⁴S¹⁶O in the ground X³Σ^? state has been observed using five optically pumped laser lines as sources. The isotopic sulfur monoxide radical was produced by the reaction of oxygen gas with sulfur vaporized from an oven. The construction and design of such an oven have been discussed. A merged least squares fit of the earlier EPR and microwave results, and the present data yield better-determined molecular constants.     

Exposure of monomolecular lithographic patterns to ambient: an X-ray photoemission spectromicroscopy study

Patterned self-assembled monolayers (SAMs) of alkanethiolates (AT) on Au and Ag substrates were imaged and characterized by scanning photoelectron microscopy (SPEM). The patterns were prepared in situ by direct writing with the zone-plate-focused X-ray beam provided by the SPEM station. Whereas both AT/Au and AT/Ag behaved alike upon the irradiation, which resulted in similar contrasts in the fabricated patterns and similar microspot spectra from the irradiated areas, the intensity relationship between the patterned and nonpatterned areas changed by different pathways for the Au and Ag substrates after the exposure of the patterns to ambient. The SPEM data imply that weakly bound molecular fragments are desorbed from the irradiated areas upon air exposure in the case of Ag, whereas adsorption of airborne molecules from ambient occurs for the Au substrate. The origin of the observed differences is presumably related to the specific branching patterns of irradiation-induced modification of AT/Au and AT/Ag.     

Scaling behavior of the first arrival time of a random-walking magnetic domain

We report a universal scaling behavior of the first arrival time of a traveling magnetic domain wall into a finite space-time observation window of a magneto-optical microscope enabling direct visualization of a Barkhausen avalanche in real time. The first arrival time of the traveling magnetic domain wall exhibits a nontrivial fluctuation and its statistical distribution is described by universal power-law scaling with scaling exponents of 1.34+/-0.07 for CoCr and CoCrPt films, despite their quite different domain evolution patterns. Numerical simulation of the first arrival time with an assumption that the magnetic domain wall traveled as a random walker well matches our experimentally observed scaling behavior, providing an experimental support for the random-walking model of traveling magnetic domain walls.     

Three Dimensionality and Orbital Characters of the Fermi Surface in (Tl,Rb)_{y}Fe_{2-x}Se_{2}

We report a comprehensive angle-resolved photoemission spectroscopy study of the tridimensional electronic bands in the recently discovered Fe selenide superconductor (Tl,Rb)_{y}Fe_{2-x}Se_{2} (T_{c}=32 K). We determined the orbital characters and the k_{z} dependence of the low energy electronic structure by tuning the polarization and the energy of the incident photons. We observed a small 3D electron Fermi surface pocket near the Brillouin zone center and a 2D like electron Fermi surface pocket near the zone boundary. The photon energy dependence, the polarization analysis and the local-density approximation calculations suggest a significant contribution from the Se 4p_{z} and Fe 3d_{xy} orbitals to the small electron pocket. We argue that the emergence of Se 4p_{z} states might be the cause of the different magnetic properties between Fe chalcogenides and Fe pnictides.