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  • 1
    ISSN: 1090-6509
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The fluorescence resonance energy-transfer (FRET) process is investigated between donor dye molecules deposited on the sample surface and acceptor dye molecules deposited on the tips of scanning near-field and atomic force microscopes. The FRET process was observed only when the tip acquired contact with the sample and took place in regions of sizes of only a few tens of nanometers with only a few thousands (or even hundreds) of molecules involved. The dependence of the FRET intensity on the tip-sample acting force is recorded and interpreted. In relation to the obtained results, the construction of a previously proposed one-atom FRET SNOM is described.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4128-4133 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A red wing in the absorption of H2O in the first continuum which extends beyond 200 nm is induced by the matrix. A threshold energy of 6.95 eV is found for the quantum efficiency of permanent dissociation of H2O into OH and H. This corresponds to an additional barrier of 1.8 eV due to the matrix cage. The barrier is attributed to the sum of repulsive H–Ar pair potentials in an interstitial site of D3 symmetry, which has to be surmounted by the H atom on the way from the initial substitutional H2O site to the final stable Oh site of the abstracted H atom.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 9206-9207 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5993-6005 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Electronic and vibrational relaxation of NO in Ar, Kr and Xe matrices has been studied using excitation spectra and time and energy resolved emission spectra. In addition to the vibrationally relaxed emissions from a 4Π(v=0), B 2Π(v=0) and A 2Σ+(v=0) in Ar and Kr matrices, B(v=5 and 7) emissions are observed in Ar matrices. In Xe matrices, only Rydberg A 2Σ+(v=0) fluorescence is observed. Nonradiative Rydberg–valence transitions are observed in all matrices and valence–Rydberg transitions only in Ar matrices. The intensity ratios IA/IB/Ia are ∼3/9/88 in Ar, ∼9/3/88 in Kr, and ∼2–5/0/0 in Xe matrices. The quantum efficiency for total luminescence being near unity in Ar and Kr matrices. The branching ratios for intramolecular relaxation between Rydberg and valence states are described in terms of a model which combines the intramolecular Franck–Condon factors with the spectroscopically determined phonon Franck–Condon factors and solvent enhanced spin–orbit matrix elements. The latter increase from Ar to Xe matrices. This increase is rationalized in terms of a semiempirical model for the heavy-atom effect on spin–orbit mixing. Weak Rydberg–Rydberg relaxation by a Δv=2 step in Ar and a Δv=1 step in Kr is also observed and interpreted in terms of a resonant Förster–Dexter-type energy transfer. Finally in Xenon matrices, a strongly nonresonant energy transfer from the n=l exciton of solid xenon to the A(v=0) Rydberg level is observed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 1277-1284 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Fluorescence spectra from the Rydberg A 2Σ+ (v=0) level of NO trapped in Ne, Ar, Kr, and Xe matrices have been obtained for two different sites. The main site is characterized by broad A(0,v‘) bands (FWHM(approximately-equal-to)80 meV), blue gas-to-matrix shifts of 70 to 300 meV, and by absorption–emission Stokes shifts of 300 meV in Xe to 800 meV in Ne matrices. The line shapes and Stokes shifts are treated within a configuration coordinate model by a moment analysis. A linear and quadratic coupling is invoked with relaxation energies ranging for the excited state from 160 meV in Xe to 540 meV in Ne and for the ground state from 150 meV in Xe to 280 meV in Ne and an increase of the cage radius of 3% in Xe to 15% in Ne. The "red'' site fluorescence shows emission bands with matrix shifts of −140 meV in Xe to 80 meV in Ne and absorption–emission Stokes shifts of 210 meV in Xe to 830 meV in Ne. Red site "hot'' A (v=1) fluorescence is also observed. Red sites are attributed to local disorder around the molecule in Ar, Kr, and Xe matrices and to hexagonal close packed (hcp) pockets within the face centered cubic (fcc) lattice in the case of Ne matrices.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 3458-3462 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The term values of the ground and excited Rydberg states of alkali metal atoms trapped in rare gas matrices are derived from an empirical model potential. The analytical potential smoothly connects the Coulomb potential near the core with the shielded Coulomb potential beyond the first shells of surrounding matrix atoms. The potential does not depend on the specific dopant and is determined for each rare gas matrix in a unique way from the polarization energy of the crystal by the ionic core P+ and from the electron affinity V0. The predicted transition energies agree with the experimental data within 0.1 to 0.2 eV.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 2472-2482 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Several new progressions consisting of broadbands have been observed in the absorption spectra of NO trapped in rare gas matrices. They are identified as the blue shifted transitions to the n=3 (A 2Σ+,C 2Π,D 2Σ+) and n=4 (E 2Σ+,K 2Π,M 2Σ+) Rydberg states of NO in Ne matrices and to the n=3 Rydberg states in Ar, Kr, and Xe matrices. Linewidths (50 to 180 meV) and matrix shifts (0.3 to 1.2 eV) decrease from neon to xenon matrices. For each matrix, the shifts decrease according to the symmetry of the excited state orbital, in the sequence sσ–pσ–pπ. An attempt to apply the quantum defect formula with values, for the Rydberg constant and the ionization potential of the matrix isolated molecule taken from literature, fails to describe the vertical transition energies of n=3 and n=4 states in neon matrices. On the other hand, using the adiabatic energies of 3sσ and 4sσ states to generate a series shows that the vertical transitions of n≥5 states lie in the ionization continuum. This could explain the nonobservation of n〉4 states in Ne matrices. In the heavier matrices, this model predicts n=4 states but their existence is not borne out by experiment. The Wannier model also fails to describe these transitions.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 3245-3251 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A threshold near 6.8 eV is observed for the dissociation of H2O (and D2O) via the repulsive A˜(1B1) potential in rare gas matrices. The threshold varies within 0.2 eV for exchange of Kr with Ar matrix, upon deuteration and with temperature. The observations are consistent with a prompt dissociation across matrix induced barriers of about 1.8 eV caused by the repulsive hydrogen–rare gas potentials. The increase of dissociation efficiency above threshold and its variation with matrix and isotope substitution seen in the experiments is rationalized by the mass dependence of energy exchange between fragment and matrix and the dependence of the accessible exit cone on kinetic energy. A strong increase in the dissociation efficiency with temperature is observed which is different for Ar and Kr.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 7083-7093 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: New time and energy resolved data on vibrationally relaxed and unrelaxed emissions from the valence a 4 Π(v=0), B 2 Π(v=0,3,4,5), and the Rydberg A 2 Σ+ (v=0,1,2) states of NO in Ne matrices are reported. Rydberg ↔ valence and valence ↔ valence nonradiative transitions are identified. The Rydberg → valence transitions are seen to occur after lattice relaxation accommodating the Rydberg orbital. The branching ratios for intramolecular relaxation and the measured lifetimes are described in terms of a model which combines the intramolecular spin–orbit matrix elements and Franck–Condon factors with the spectroscopically determined phonon Franck–Condon factors. For the levels B 2 Π(v=5,6), a Förster–Dexter-type energy transfer between NO molecules is also invoked in the description of the relaxation cascade.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 4542-4552 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The structural changes due to formation of electronic bubbles in solid D2 are investigated by means of fluorescence, fluorescence-excitation, and fluorescence-depletion spectroscopy of the lowest Rydberg state, A 2Σ+(3sσ), of the NO impurity. The A←X band is strongly blueshifted (∼0.7 eV) with respect to the gas phase and shows a very broad (full width at half maximum ∼2000 cm−1) and asymmetric profile. The shift results from the strong repulsion due to the overlap of the extended Rydberg orbital with the matrix species, while the width and asymmetry are governed by quantum effects on the ground-state intermolecular wave function. Fluorescence occurs with large absorption-emission Stokes shifts, bringing the A-state emission energy to its gas-phase value, which indicates a very loose cavity around the excited molecule. A line-shape analysis of the A-X absorption and emission bands allows us to extract one-dimensional intermolecular NO-matrix potentials of both involved states. We estimate the bubble radius to ∼5 Å, in good agreement with values from the literature for the bubble radius of the solvated electron. Fluorescence-depletion spectra of the A state are also presented along with the ground-state transitions to the higher C 2Π(3pπ) and D 2Σ+(3pσ) states. They are used to generate intermolecular potentials for the C and D states, which are essential ingredients for ultrafast pump–probe experiments of the bubble dynamics. The results obtained for D2 matrices are compared with those previously published for H2 matrices. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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