54 research outputs found
Photodissociation dynamics of the iodide-uracil (I-U) complex
Photofragment action spectroscopy and femtosecond time-resolved photoelectron imaging are utilized to probe the dissociation channels in iodide-uracil (I− ⋅ U) binary clusters upon photoexcitation. The photofragment action spectra show strong I− and weak [U- H]− ion signal upon photoexcitation. The action spectra show two bands for I− and [U- H]− production peaking around 4.0 and 4.8 eV. Time-resolved experiments measured the rate of I− production resulting from excitation of the two bands. At 4.03 eV and 4.72 eV, the photoelectron signal from I− exhibits rise times of 86 ± 7 ps and 36 ± 3 ps, respectively. Electronic structure calculations indicate that the lower energy band, which encompasses the vertical detachment energy (4.11 eV) of I−U, corresponds to excitation of a dipole-bound state of the complex, while the higher energy band is primarily a π-π∗ excitation on the uracil moiety. Although the nature of the two excited states is very different, the long lifetimes for I− production suggest that this channel results from internal conversion to the I− ⋅ U ground state followed by evaporation of I−. This hypothesis was tested by comparing the dissociation rates to Rice-Ramsperger-Kassel-Marcus calculations
Determinisitic Optical Fock State Generation
We present a scheme for the deterministic generation of N-photon Fock states
from N three-level atoms in a high-finesse optical cavity. The method applies
an external laser pulsethat generates an -photon output state while
adiabatically keeping the atom-cavity system within a subspace of optically
dark states. We present analytical estimates of the error due to amplitude
leakage from these dark states for general N, and compare it with explicit
results of numerical simulations for N \leq 5. The method is shown to provide a
robust source of N-photon states under a variety of experimental conditions and
is suitable for experimental implementation using a cloud of cold atoms
magnetically trapped in a cavity. The resulting N-photon states have potential
applications in fundamental studies of non-classical states and in quantum
information processing.Comment: 25 pages, 9 figure
?Room for improvement? ? some personal reflections on writing about children's special educational needs
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