Dissociation energies of AgRG (RG = Ar, Kr, Xe) and AgO molecules from velocity map imaging studies

The near ultraviolet photodissociation dynamics of silver atom rare gas dimers have been studied by velocity map imaging. AgRG (RG = Ar, Kr, Xe) species generated by laser ablation are excited in the region of the C <- X continuum leading to direct, near threshold dissociation generating Ag* (2P3/2) + RG (1S0) products. Images recorded at excitation wavelengths throughout the C <- X continuum, coupled with known atomic energy levels, permit determination of the ground X (2SIGMA+) state dissociation energies of 85.9 +/- 23.4 cm-1 (AgAr), 149.3 +/- 22.4 cm-1 (AgKr) and 256.3 +/- 16.0 cm-1 (AgXe). Three additional photolysis processes, each yielding Ag atom photoproducts, are observed in the same spectral region. Two of these are markedly enhanced in intensity upon seeding the molecular beam with nitrous oxide, and are assigned to photodissociation of AgO at the two photon level. These features yield an improved ground state dissociation energy for AgO of 15965 +/- 81 cm-1, which is in good agreement with high level calculations. The third process results in Ag atom fragments whose kinetic energy shows anomalously weak photon energy dependence and is assigned tentatively to dissociative ionization of the silver dimer Ag2

Atomic Undercoordination in Ag Islands on Ru(0001) Grown via Size-Selected Cluster Deposition: An Experimental and Theoretical High-Resolution Core-Level Photoemission Study

The possibility of depositing precisely mass-selected Ag clusters (Ag1, Ag3, and Ag7) on Ru(0001) was instrumental in determining the importance of the in-plane coordination number (CN) and allowed us to establish a linear dependence of the Ag 3d5/2 core-level shift on CN. The fast cluster surface diffusion at room temperature, caused by the low interaction between silver and ruthenium, leads to the formation of islands with a low degree of ordering, as evidenced by the high density of low-coordinated atomic configurations, in particular CN = 4 and 5. On the contrary, islands formed upon Ag7 deposition show a higher density of atoms with CN = 6, thus indicating the formation of islands with a close-packed atomic arrangement. This combined experimental and theoretical approach, when applied to clusters of different elements, offers the perspective to reveal nonequivalent local configurations in two-dimensional (2D) materials grown using different building blocks, with potential implications in understanding electronic and reactivity properties at the atomic level

Device-Compatible Chiroptical Surfaces through Self-Assembly of Enantiopure Allenes

Chiroptical methods have been proven to be superior compared to their achiral counterparts for the structural elucidation of many compounds. To expand the use of chiroptical systems to everyday applications, the development of functional materials exhibiting intense chiroptical responses is essential. Particularly, tailored and robust interfaces compatible with standard device operation conditions are required. Herein, we present the design and synthesis of chiral allenes and their use for the functionalization of gold surfaces. The self-assembly results in a monolayer-thin room-temperature-stable upstanding chiral architecture as ascertained by ellipsometry, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure. Moreover, these nanostructures anchored to device-compatible substrates feature intense chiroptical second harmonic generation. Both straightforward preparation of the device-compatible interfaces along with their chiroptical nature provide major prospects for everyday applications

Imaging the photodissociation dynamics of neutral metal clusters: copper dimer, Cu2, and copper oxide, CuO.

The spectroscopy and UV photodissociation dynamics of Cu2 and CuO have been studied using a combination of one- and two-colour excitation and velocity map imaging. Resonant excitation of Cu2 via the J ← X (1)Σg(+) transition leads to significant fragmentation which is interpreted in terms of a combination of direct dissociation of Cu2(+ 2)Π produced in the resonant two-photon ionization process and dissociation of excited Cu2 states above the ionization threshold. By fitting of the kinetic energy release spectra obtained from the velocity map images, we determine a value for the dissociation energy of the cation of D0 (Cu2(+), X (2)Σg(+)) of 1.713 ± 0.025 eV, which, when combined with known ionization energies, yields D0 (Cu2, X (1)Σg(+)) = 1.886 ± 0.026 eV. In other experiments, resonant two colour (1 + 1') excitation of CuO via a range of excited states (C, D, F, H), yields unusually simple VMI images indicating fragmentation into a single dissociation channel which has been identified as Cu* (2)D3/2 + O* (1)D. Taken together, this data gives a CuO bond dissociation energy of 3.041 ± 0.030 eV. Finally, the production of Cu2(+) with kinetic energy = 705 ± 75 cm(-1) is tentatively interpreted as photolysis of Cu3 yielding Cu* + Cu2 X (1)Σg(+) from which a dissociation energy of Cu3 of 0.605 ± 0.030 eV is deduced

Imaging the photodissociation dynamics of neutral metal clusters: copper dimer, Cu2, and copper oxide, CuO.

The spectroscopy and UV photodissociation dynamics of Cu2 and CuO have been studied using a combination of one- and two-colour excitation and velocity map imaging. Resonant excitation of Cu2 via the J ← X (1)Σg(+) transition leads to significant fragmentation which is interpreted in terms of a combination of direct dissociation of Cu2(+ 2)Π produced in the resonant two-photon ionization process and dissociation of excited Cu2 states above the ionization threshold. By fitting of the kinetic energy release spectra obtained from the velocity map images, we determine a value for the dissociation energy of the cation of D0 (Cu2(+), X (2)Σg(+)) of 1.713 ± 0.025 eV, which, when combined with known ionization energies, yields D0 (Cu2, X (1)Σg(+)) = 1.886 ± 0.026 eV. In other experiments, resonant two colour (1 + 1') excitation of CuO via a range of excited states (C, D, F, H), yields unusually simple VMI images indicating fragmentation into a single dissociation channel which has been identified as Cu* (2)D3/2 + O* (1)D. Taken together, this data gives a CuO bond dissociation energy of 3.041 ± 0.030 eV. Finally, the production of Cu2(+) with kinetic energy = 705 ± 75 cm(-1) is tentatively interpreted as photolysis of Cu3 yielding Cu* + Cu2 X (1)Σg(+) from which a dissociation energy of Cu3 of 0.605 ± 0.030 eV is deduced

Infrared spectroscopy of gas-phase M(+)(CO2)n (M = Co, Rh, Ir) ion-molecule complexes

The structures of gas-phase M(+)(CO2)n (M = Co, Rh, Ir; n = 2-15) ion-molecule complexes have been investigated using a combination of infrared resonance-enhanced photodissociation (IR-REPD) spectroscopy and density functional theory. The results provide insight into fundamental metal ion-CO2 interactions, highlighting the trends with increasing ligand number and with different group 9 ions. Spectra have been recorded in the region of the CO2 asymmetric stretch around 2350 cm(-1) using the inert messenger technique and their interpretation has been aided by comparison with simulated infrared spectra of calculated low-energy isomeric structures. All vibrational bands in the smaller complexes are blue-shifted relative to the asymmetric stretch in free CO2, consistent with direct binding to the metal center dominated by charge-quadrupole interactions. For all three metal ions, a core [M(+)(CO2)2] structure is identified to which subsequent ligands are less strongly bound. No evidence is observed in this size regime for complete activation or insertion reactions

Dissociation energies of Ag-RG (RG = Ar, Kr, Xe) and AgO molecules from velocity map imaging studies.

The near ultraviolet photodissociation dynamics of silver atom-rare gas dimers have been studied by velocity map imaging. Ag-RG (RG = Ar, Kr, Xe) species generated by laser ablation are excited in the region of the C ((2)Σ(+))←X ((2)Σ(+)) continuum leading to direct, near-threshold dissociation generating Ag* ((2)P3/2) + RG ((1)S0) products. Images recorded at excitation wavelengths throughout the C ((2)Σ(+))←X ((2)Σ(+)) continuum, coupled with known atomic energy levels, permit determination of the ground X ((2)Σ(+)) state dissociation energies of 85.9 ± 23.4 cm(-1) (Ag-Ar), 149.3 ± 22.4 cm(-1) (Ag-Kr), and 256.3 ± 16.0 cm(-1) (Ag-Xe). Three additional photolysis processes, each yielding Ag atom photoproducts, are observed in the same spectral region. Two of these are markedly enhanced in intensity upon seeding the molecular beam with nitrous oxide, and are assigned to photodissociation of AgO at the two-photon level. These features yield an improved ground state dissociation energy for AgO of 15 965 ± 81 cm(-1), which is in good agreement with high level calculations. The third process results in Ag atom fragments whose kinetic energy shows anomalously weak photon energy dependence and is assigned tentatively to dissociative ionization of the silver dimer Ag2