Surface-enhanced raman scattering from silver-cyanide and silver-thiocyanate vibrations and the importance of adatoms

Surface-enhanced Raman scattering (SERS) has been studied for silver-cyanide and 3-thiocyanate vibrations at 221 and 2111 cm^?1 and at 218 and 2132 cm^?1, respectively. We report evidence that besides large-scale surface roughness the presence of adatoms is mandatory in order to obtain SERS.     

Rotationally inelastic scattering from surfaces CO(g) + LiF(OO1)

The rotationally inelastic scattering of a supersonic, rotanonally cold (T_rot^I = 4–30 k) CO molecular beam from a clean LiF(001) surface has been investigated by VUV laser-induced fluorescence. Rotational accommodation was incomplete for surface temperatures 350 <T_s < 900 K. The degree of accommodation decreased with T_s and was independent of collision energy.     

The temperature dependence of the HO2 + HO2 reaction

The temperature dependence of the rate constant for the reaction HO₂ + HO₂ → H₂O₂ + O₂ (2k₁) has been determined using flash photolysis techniques, over the temperature range 298–510 K, in a nitrogen diluent at a total pressure of 700 Torr. The overall second order state constant is given by k₁ = (4.14 ± 1.15) × 10^?13 exp[(630 ± 115)/T] cm³ molecule^?1 s^?1, where the quoted errors refer to one standard deviation. This result is compared with previous findings and the negative activation energy is shown to be consistent with the observation that the rate constant is pressure dependent at 700 Torr.     

Energy transfer rates for vibrationally excited gas-phase azulene in the electronic ground state

Gas-phase azulene molecules were prepared with 17200 cm^?1 vibrational energy in the S₀ state by laser excitation of the S₁ state and subsequent internal conversion. Rates of vibrational energy removal (for several collision partners) were determined from the decay of the CH-stretch fluorescence at 3.3 μm. A stepladder model indicates each azulene-azulene collision removes 3500 cm^?1 of vibrational energy.     

Vibrattonal excitation of molecules by collisions with “hot” hydrogen atoms from laser photolysis

Excimer laser (ArF) photolysis of diatomic and triatomic hydrides produces hydrogen atoms with translational energies in excess of 15000 cm^?1 per atom. Subsequent collisions of these “hot” atoms with CO₂ and N₂O produces vibrationally excited molecules which can be detected by their characteristic infrared emission.     

A statistical model for the fragmentation of benzene by multiphotoionization

A statistical products phase space model for the (multi) photon fragmentation/ionization of polyatomic molecules in strong laser fields is proposed and tested on benzene. The mechanism assumes multiple dissociations and branchings starting with energy rich benzene ions. Calculated and experimental fragment mass patterns versus laser fluence are shown to be in good agreement.     

Comparison of PBDE congener profiles and concentration levels in human specimens from China and the US and identification of human exposure sources

In an effort to investigate the status of human exposure to PBDEs in China,available monitoring data in human specimens(including breast milk,serums,and blood) was collected from the general population as well as specific groups that are occupationally exposed.PBDEs exposure profiles and concentration levels were compared with their counterparts in the United States of America.It was found that PBDE burdens in general Chinese population are one order lower and have different congener profiles from that in t...     

Minimum degree condition for a graph to be knitted

For a positive integer $k$, a graph is $k$-knitted if for each subset $S$ of $k$ vertices, and every partition of $S$ into (disjoint) parts $S_1,\dots ,S_t$ for some $t\ge 1$, one can find disjoint connected subgraphs $C_1,\dots ,C_t$ such that $C_i$ contains $S_i$ for each $i\in \left[t\right]?\{1,2,\dots ,t\}$. In this article, we show that if the minimum degree of an $n$-vertex graph $G$ is at least $n∕2+k∕2?1$ when $n\ge 2k+3$, then $G$ is $k$-knitted. The minimum degree is sharp. As a corollary, we obtain that $k$-contraction-critical graphs are $?\frac{k}{8}?$-connected.     

DP-3-coloring of some planar graphs

In this article, we use a unified approach to prove several classes of planar graphs are DP-3-colorable, which extend the corresponding results on 3-choosability.     

Ab initio computations on small copper compounds-CuO

Ab initio computations on CuO were performed with the Hartree-Fock method and a proper dissociation MC SCF procedure. In particular the influence of the GTO basis set for Cu in molecular computations has been studied. A potential energy curve and a Mulliken population analysis are presented. The equilibrium bond length is predicted reasonably well but the dissociation energy is only a fraction of the observed value. The bond appears to be a slightly ionic δ-type bond, in which metal 3d orbitals participate only to a small extent.