Exciton relaxation processes in J-aggregates of 3,3′,9-triethyl-5,5′-dichlorothiacarbocyanine iodide (TDC) dye have been studied by means of site-selective, steady-state and time-resolved ...spectroscopy. We found that TDC forms three different types of J-aggregates (J
1,J
2, and J
3) in frozen solutions. Fluorescence polarization measurements showed that exciton diffusion between randomly oriented segments of aggregates plays a minor role in exciton relaxation. Optical properties of J
3-aggregate fluorescent states are well described by the theoretical model of barrierless self-trapping of an excitation in a strictly one-dimensional discrete lattice. Upon optical excitation J
3-aggregates also show thermally activated transformation to J
2-aggregates. The height of the related potential barrier is approximately equal to 30 cm
−1. Hence, two different exciton relaxation processes are proposed to take place in the system under study: barrierless self-trapping in J
3-aggregates and thermally activated J
3 → J
2 photorearrangement.
Recent discussions about the origin of the Gallium Anomaly have motivated a remeasurement of the half life of \(^{71}\)Ge. We have conducted three separate measurements using dedicated planar Ge ...detectors: one with \(^{55}\)Fe as a standard, one with \(^{57}\)Co as a standard, and one stand alone 71Ge measurement. Our results yield a half life of 11.468 +- 0.008 days, which is consistent with but significantly more precise than the currently accepted value. With this experiment, the potential explanation of the Gallium Anomaly being due to an unexpectedly long \(^{71}\)Ge half life has been ruled out, leaving the origin of the anomaly as an open question.
We report the results of a search for neutrinoless double-beta decay in a 9.8 kg yr exposure of (130)Te using a bolometric detector array, CUORE-0. The characteristic detector energy resolution and ...background level in the region of interest are 5.1±0.3 keV FWHM and 0.058±0.004(stat)±0.002(syst)counts/(keV kg yr), respectively. The median 90% C.L. lower-limit half-life sensitivity of the experiment is 2.9×10(24) yr and surpasses the sensitivity of previous searches. We find no evidence for neutrinoless double-beta decay of (130)Te and place a Bayesian lower bound on the decay half-life, T(1/2)(0ν)>2.7×10(24) yr at 90% C.L. Combining CUORE-0 data with the 19.75 kg yr exposure of (130)Te from the Cuoricino experiment we obtain T(1/2)(0ν)>4.0×10(24) yr at 90% C.L. (Bayesian), the most stringent limit to date on this half-life. Using a range of nuclear matrix element estimates we interpret this as a limit on the effective Majorana neutrino mass, m(ββ)<270-760 meV.
Analytical results are obtained for the non-dispersive and dispersive kinetics of persistent hole burning. Model calculations are used to interpret some hole burning data and new experiments with ...protoporphyrin salt, a system involving electron transfer.
The experimental absorption spectra of J-aggregates of the carbocyanine dye THIATS and TDC were fitted to a segment and a continuous energy disorder (CED) model. From 6 K to room temperature the best ...fits were obtained using an exponential distribution of segment lengths. Both models gave equally good fits when the average length in the segment model corresponded to the average localization length in the CED model. At room temperature homogeneous broadening or/and an enhanced contribution of the off-diagonal disorder must be taken into account.
An array of twelve 0.28 kg lithium molybdate (LMO) low-temperature bolometers
equipped with 16 bolometric Ge light detectors, aiming at optimization of
detector structure for CROSS and CUPID ...double-beta decay experiments, was
constructed and tested in a low-background pulse-tube-based cryostat at the
Canfranc underground laboratory in Spain. Performance of the scintillating
bolometers was studied depending on the size of phonon NTD-Ge sensors glued to
both LMO and Ge absorbers, shape of the Ge light detectors (circular vs.
square, from two suppliers), in different light collection conditions (with and
without reflector, with aluminum coated LMO crystal surface). The scintillating
bolometer array was operated over 8 months in the low-background conditions
that allowed to probe a very low, $\mu$Bq/kg, level of the LMO crystals
radioactive contamination by $^{228}$Th and $^{226}$Ra.
We performed selective laser excitation of fluorescence of thin films of poly(
p-phenylene) (PPP) at room and liquid helium temperatures. Monochromatic laser excitation becomes selective upon ...excitation below a threshold frequency of 22 400 cm
−1 in the low-energy tail of the fluorescence excitation band, 2200 cm
−1 below the maximum of the excitation spectrum. The experimental results are interpreted on the basis of model calculations.
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