ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • American Institute of Physics (AIP)  (6)
  • 1
    Electronic Resource
    Electronic Resource
    Calculation of the Si–H bond energies for the monohydride phase of Si(100) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 8652-8654 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ab initio calculations are carried out on Si9H12, Si9H13, and Si9H14 clusters, chosen to model the Si(100)–(2×1) reconstructed surface and its hydrides. A value of 56 kcal/mol is obtained for the energy of the recombinative hydrogen desorption. The energies required to remove the first and second H atoms from a doubly-occupied site are 81 and 76 kcal/mol, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461245
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Mode-selective photoisomerization in 5-hydroxytropolone. II. Theory (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 5260-5270 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ab initio calculations are used to explore the ground-state potential energy surface for the syn–anti photoisomerization reaction of 5-hydroxytropolone (5-HOTrOH). Two reaction coordinates are identified, involving 2-OH tunneling and 5-OH torsion. Hartree–Fock (HF) and perturbation theory (at the MP2 level) have been used to calculate the stationary points on the two-dimensional surface associated with these coordinates. Similar calculations on the parent molecule tropolone are carried out for comparison. As observed in previous studies, the 2-OH tunneling barrier drops dramatically at the MP2 level which includes electron correlation. Vibrational frequency calculations are carried out for both tropolone and 5-HOTrOH at the HF/6-31G** and MP2/6-31G** levels in order to correlate the modes with those observed experimentally. A method is introduced for evaluating which normal coordinates should be most strongly coupled to a given reaction coordinate. Normalized, mass-weighted intrinsic and direct reaction coordinates similar in form to the normal coordinates are devised by projecting atomic displacements from the reactant structure toward a transition state (intrinsic) or product (direct) structure. These serve as limiting cases for the initial projections of the multidimensional reaction trajectories. The intrinsic and direct reaction coordinates are then expanded in the basis set of normal coordinates to obtain coefficients of expansion of the reaction coordinates in this basis set. This simple scheme highlights the subset of normal coordinates which are important in promoting reaction by H-atom tunneling or O–H torsion. In 5-HOTrOH, an in-plane mode calculated at 348 cm−1 has a large coefficient of expansion along both intrinsic and direct reaction coordinates. This mode is assigned as the "promoter mode'' W observed in the experimental study of paper I. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469251
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Fluorescence-dip infrared spectroscopy of tropolone and tropolone-OD (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 2595-2604 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Fluorescence-dip infrared spectroscopy (FDIRS) is employed to record the infrared spectra of the isolated, jet-cooled tropolone molecule (TrOH) and its singly deuterated isotopomer TrOD in the O–H and C–H stretch regions. The ability of the method to monitor a single ground-state level enables the acquisition of spectra out of the lower and upper levels of the zero-point tunneling doublet free from interference from one another. The high power of the optical parametric oscillator used for infrared generation produces FDIR spectra with good signal-to-noise despite the weak intensity of the C–H and O–H stretch transitions in tropolone. The expectation that both spectra will exhibit two OH stretch transitions separated by the OH(v=1) tunneling splitting is only partially verified in the present study. The spectra of TrOH are compared with those from deuterated tropolone (TrOD) to assign transitions due to C–H and O–H, which are in close proximity in TrOH. The appearance of the spectra out of lower (a1 symmetry) and upper (b2 symmetry) tunneling levels are surprisingly similar. Two sharp transitions at 3134.9 cm−1 (out of the a1 tunneling level) and 3133.9 cm−1 (out of the b2 tunneling level) are separated by the ground-state tunneling splitting (0.99 cm−1), and thereby terminate in the same upper state tunneling level. Their similar intensities relative to the C–H stretch transitions indicate that the y- and z-polarized transitions are of comparable intensity, as predicted by ab initio calculations. The corresponding transitions to the other member of the upper state tunneling doublet are not clearly assigned by the present study, but the broad absorptions centered about 12 cm−1 below the assigned transitions are suggested as the most likely possibility for the missing transitions. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472119
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Fluorescence-dip infrared spectroscopy of the tropolone-H2O complex (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 2605-2617 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Fluorescence dip infrared spectroscopy (FDIRS) is used to probe the effect of a solvent water molecule on intramolecular H-atom tunneling in tropolone. As with the bare molecule discussed in paper I, the FDIR spectrum of the tropolone-H2O complex is recorded in the O–H and C–H stretch regions. Three OH stretch fundamentals are observed in the spectrum, and can be assigned nominally to a free OH stretch of the water molecule (3724 cm−1), a hydrogen bonded OH stretch of water (3506 cm−1), and the OH stretch of tropolone (∼3150 cm−1). The breadth and complexity of the bands is highly mode specific. The free OH stretch transition is sharp (1.8 cm−1 FWHM) and has weak combination bands built on it at +73 and +1600 cm−1. The former is assigned to a combination band with the in-plane bending mode of the tropolone-H2O hydrogen bond, while the latter is the free OH/intramolecular water bend combination band. The water hydrogen-bonded OH fundamental is also a sharp transition which, after correction for the decreased infrared power at its frequency, is clearly the strongest transition in the spectrum. It is flanked by three close-lying satellite bands 13, 23, and 34 cm−1 above it, and also supports a weak combination band at +69 cm−1 due to the in-plane intermolecular bending mode. The tropolone OH absorption is in the same frequency region as in the bare molecule, but broadened to over 100 cm−1 in TrOH–H2O. Distinct substructure in the band is present, with spacings reminiscent of those in the water H-bonded OH stretch region. Ab initio calculations on tropolone-H2O are carried out at both the MP2 and Becke3LYP levels of theory. Two isomers with similar binding energies and vibrational frequencies are identified. In one isomer (isomer I), the water molecule serves as a hydrogen-bonded bridge between the tropolone OH and keto groups. In the other (isomer II), the water molecule is exterior to the tropolone and hydrogen bonded to the keto oxygen. The experimental evidence does not conclusively distinguish between these two possibilities, though the exterior structure seems somewhat more in keeping with the data as a whole. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472125
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Photochemistry of (OCS)n− cluster ions (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 1264-1270 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the photochemistry of (OCS)n− cluster ions following 395 nm (n=2–28) and 790 nm (n=2–4) excitation. In marked contrast to (CO2)n−, extensive bond breaking and rearrangement is observed. Three types of ionic products are identified: S2−(OCS)k, S−(OCS)k/OCS2−(OCS)k−1, and (OCS)k−. For n〈16, 395 nm dissociation is dominated by S2−-based fragments, supporting the theoretical prediction of a cluster core with a C2v (OCS)2− dimer structure and covalent C–C and S–S bonds. A shift in the branching ratio in favor of S−-based products is observed near n=16, consistent with an opening of the photodissociation pathway of OCS− core-based clusters. These monomer-based cluster ions may coexist with the dimer-based clusters over a range of n, but electron detachment completely dominates photodissociation as long as their vertical electron detachment energy, increasing with addition of each solvent molecule, is less then the photon energy. An (OCS)2− conformer of C2 symmetry with a covalent C–C bond is believed to be responsible for 790 nm dissociation of (OCS)2−, yielding primarily OCS− products. The yield of OCS−, and thus the importance of the C2 form of (OCS)2− cluster core, decreases with increasing n, perhaps due to more favorable solvation of the C2v form of (OCS)2− and/or a solvent-induced increase in the rate of interconversion of conformers. The (OCS)k− products observed in 395 nm photodissociation of the larger (n≥7) clusters are attributed to photofragment caging. Formation and dissociation mechanisms of clusters with different core types are discussed. The photochemical properties of (OCS)n− are compared to those of the isovalent (CO2)n− and (CS2)n− species. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476677
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Rearrangement pathways of the water trimer and tetramer anions (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 3612-3616 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Minimum energy pathways for the rearrangement of the anions of the water trimer and tetramer anions between their cyclic and chain structures were investigated by means of ab initio electronic structure calculations, coupled with nudged elastic band optimizations. The rearrangements of both anions are found to proceed by opening of the cyclic structure and reorientation of the water molecules as the excess electron migrates to the terminal water fragment with the dangling hydrogens. The activation energies for the cyclic→chain rearrangements are calculated to be 0.11 and 0.32 eV for (H2O)3− and (H2O)4−, respectively. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1447903
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...