Optical parametric oscillation in periodically poled lithium niobate driven by a diode-pumped Q-switched erbium fiber laser

We describe what is to our knowledge the first nanosecond periodically poled lithium niobate (PPLN) optical parametric oscillator (OPO) driven by a fiber laser. The source was frequency doubled by a PPLN sample before pumping a second, 20-mm-long, PPLN crystal. The OPO threshold was <10muJ, with pump depletions of as much as 45% and a tunable signal range of 945-1450 nm (1690-4450-nm idler range). We demonstrated 130-nm signal tuning by varying the pump wavelength and doubling crystal's temperature. Also, we achieved 15-nm tuning with all crystals at a constant temperature. The results demonstrate the potential of the fiber laser:PPLN combination for practical, versatile, and tunable sources.     

Crystal structure of terephthalaldehyde

Terephthalaldehyde forms monoclinic crystals, space group P2 ₁ /a, a = 12.698(6), b = 3.845(2), c = 14.764(3) Å, = 116.53(3)°, Z = 4, V = 645(1) ų, and Dx = 1.381(2) g cm^–3. There are two independent molecules, each located at a center of symmetry and approximately related to each other by pseudo-symmetry. In both molecules the rings are planar within experimental error. In one molecule the CHO groups are twisted out of the plane of the ring by 1.3(1)°, in the other by 0.6(1)°. Weak C–H···O hydrogen bonds occur at both independent aldehyde hydrogen atoms.     

Crystal structures of four complexes produced by reaction of copper(I) cyanide with imidazoles

Four complexes of CuCN with imidazoles have been prepared by adding the ligand to a solution of CuCN in aqueous sodium thiosulfate. The imidazole ligands used were 2-methylimidazole (mim), 1,2-dimethylimidazole (dmim), 5-chloro-1-methylimidazole (clmim), and 2-phenylimidazole (phim). Complex 1, (CuCN)(mim) is monoclinic, C2/c, a = 9.565(3), b = 7.764(5), c = 8.983(8) Å, = 96.76(3)°, Z, = 4, Complex 2, (CuCN)(dmim) is monoclinic, P2₁/c, a = 8.120(2), b = 11.796(4), c = 16.375(9) Å, , = 100.87(4)°, Z = 8. Complex 3, (CuCN) (clmim) is monoclinic, C2/c, a = 24.907(4), b = 6.894(5), c = 18.259(4) Å, = 102.79(2)°, Z = 16. Complex 4, (CuCN)(phim) is orthorhombic, Pca2₁, a = 9.204(4), b = 8.125(2), c = 26.304(6) Å, Z, = 8. Complexes 1, 2, and 4 have one-dimensional chains –Cu–CN–Cu– with an imidazole bonded to each Cu. Complex 3 has a two-dimensional sheet of CuCN, again with an imidazole bonded to each Cu. In 1 the imidazole group is disordered by a two-fold rotation approximately around the N···N direction in the imidazole group. In 3 one of the imidazole groups has a disorder involving exchange of the Cl and CH₃.     

The crystal structure of a novel product from the acid-catalyzed condensation of 1-benzylindole with acetone

The acid-catalyzed condensation of 1-benzylindole with acetone in the presence of N-phenylmaleimide gave a tetrahydrocarbazole, (4,5,10,10b-tetrahydro-5-methyl-2-phenyl-10-(phenylmethyl)pyrrolo[3,4-a]carbazole-1,3[2H, 3aH]-dione (1), as the major product and a novel spiro compound, 1,3,4,4-tetrahydro-1,1,3,3-tetramethyl-4,4-bis(phenylmethyl)-1,3(2H, 2H)-spiro[cyclopent[b]indole] (2), as the minor product. The structure of the spiro compound was determined by an X-ray crystallographic determination. The acid-catalyzed condensation of 1-benzylindole with acetone in the absence of N-phenylmaleimide gave a bisindole, (1,1-bis(phenylmethyl)-3,3-(1-methylethylidene)diindole (3), as the major product and the spiro-compound as the minor product.     

Crystal structures of p-chloro- and p-bromobenzaldehyde

p-Chloro- and p-bromobenzaldehyde form isomorphous monoclinic crystals, space groupP2 ₁/a. For p-Cl at –96°C,a=12.945(3),b=3.833(3),c=26.503(9) Å, =103.68(2)°,Z=8,V=1278(2) ų,Dx=1.461(2) g cm^–3, refinement on 2714 reflections,R=0.047. For p-Br at –96°C,a=12.754(5),b=3.919(3),c=27.317(12) Å, =103.28(3)°,Z=8,V=1329(2) ų,Dx=1.849(3) g cm^–3, refinement on 1519 reflections,R=0.062. The molecules do not differ significantly from planarity. They pack in stacks with Cl...Cl or Br...Br contacts at one end and CH...O contacts that are suggestive of hydrogen bonds at the other. There are no O...Cl or O...Br contacts.     

2,4,6‐Trifluorobenzonitrile

The title compound, C₇H₂F₃N, contains three crystallographically independent molecules in the crystal structure; two of these molecules have symmetry m and the third has symmetry mm. Each independent molecule forms a planar or approximately planar layer with its own kind. There are three different types of interlayer contacts, two of which are similar to each other, while the third is distinctly different. The packing within the layers is similar to that found in 2,5‐ and 3,6‐difluorobenzonitrile, with weak C—H...N interactions holding the molecules in the layers. The remarkable feature of this structure is the presence of more than one type of interlayer interaction.     

The sticking of H and D atoms on a graphite (0001) surface: the effects of coverage and energy dissipation

Classical trajectory methods are used to examine the trapping and sticking of H and D atoms on the graphite (0001) surface. Total energy calculations based on density functional theory are used to construct the model potential energy surface, and graphite clusters of up to 121 atoms are considered. For hydrogen to chemisorb, the bonding carbon must pucker out of the surface plane by roughly 0.4 A. For incident energies above the 0.2 eV barrier, any trapped H atoms must rapidly dissipate their excess energy into the surrounding lattice within a few vibrations of the C-H stretch in order to remain bound. For sufficiently large clusters, the C-H bond stabilizes within about 0.1 ps. The sticking probability for D at 150 K is in the range of 5%-10%, more-or-less consistent with the most recent measurements in the limit of zero coverge. Variation with isotope and substrate temperature is weak. We estimate that the sticking cross section for adsorption at the para site, directly across the sixfold carbon ring from an already adsorbed H atom, can be four or more times larger that the zero coverage sticking cross section.     

Quantitative,In Situ Visualization of Metal‐Ion Dissolution and Transport Using 1H Magnetic Resonance Imaging

Quantitative mapping of metal ions freely diffusing in solution is important across a diverse range of disciplines and is particularly significant for dissolution processes in batteries, metal corrosion, and electroplating/polishing of manufactured components. However, most current techniques are invasive, requiring sample extraction, insertion of an electrode, application of an electric potential or the inclusion of a molecular sensor. Thus, there is a need for techniques to visualize the distribution of metal ions non‐invasively, in situ, quantitatively, in three dimensions (3D) and in real time. Here we have used ¹H magnetic resonance imaging (MRI) to make quantitative 3D maps showing evolution of the distribution of Cu²⁺ ions, not directly visible by MRI, during the electrodissolution of copper, with high sensitivity and spatial resolution. The images are sensitive to the speciation of copper, the depletion of dissolved O₂ in the electrolyte and show the dissolution of Cu²⁺ ions is not uniform across the anode.