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Register a new userLochon Catalyzed D-D Fusion in Deuterated Palladium in the Solid State
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Added by
Andrew Meulenberg Jr.
Publication date
2007
fields
Physics
and research's language is
English
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Lochons (local charged bosons or local electron pairs) can form on D+ to give D- (bosonic ions) in Palladium Deuteride in the solid state. Such entities will occur at special sites or in linear channel owing to strong electron-phonon interaction or due to potential inversion on metallic electrodes. These lochons can catalyze D- - D+ fusion as a consequence of internal conversion leading to the formation of He-4 plus production of energy (Q=23.8 MeV) which is carried by the alpha particle and the ejected electron-pair. The reaction rate for this fusion process is calculated.
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This report presents the results of an experiment aimed at observation of the muon catalyzed $^3!He;d$ fusion reaction $^3!He + mu;dto^3!He;mu;dto^4!He(3.66MeV)+p(14.64MeV)+mu$ which might occur after a negative muon stop in the $D_2+^3!He$ gas mixture. The basic element of the experimental setup is a Time Projection Chamber (TPC) which can detect the incoming muons and the products of the fusion reaction. The TPC operated with the $D_2 + ^3~He (5%)$ gas mixture at $31K$ temperature. About $10^8$ $^3!He;mu;d$ molecules were produced with only 2 registered candidates for the muon catalyzed $^3!He;d$ fusion with the expected background $N_{bg}=2.2pm 0.3$ events. This gives an upper limit for the probability of the fusion decay of the $^3!He;mu;d$ molecule $P_{F}(^3!He;mu;d)leq 1.1cdot 10^{-7}$ at 90% C.L. Also presented are the measured formation rate of the $^3!He;mu;d$ molecule $lambda_{d3He}=192(3)cdot 10^6 s^{-1}$ and the probability of the fast muon transfer from the excited to the ground state of the $mu;d$ atom $q_{1S}=0.80(3)$.
The Bochum experimental enhancement of the d+d fusion rate in a deuterated metal matrix at low incident energies is explained by the quantum broadening of the momentum-energy dispersion relation and consequent modification of the high-momentum tail of the distribution function from an exponential to a power-law.
The formation of deuterated molecules is favoured at low temperatures and high densities. Therefore, the deuteration fraction D$_{frac}$ is expected to be enhanced in cold, dense prestellar cores and to decrease after protostellar birth. Previous studies have shown that the deuterated forms of species such as N2H+ (formed in the gas phase) and CH3OH (formed on grain surfaces) can be used as evolutionary indicators and to constrain their dominant formation processes and time-scales. Formaldehyde (H2CO) and its deuterated forms can be produced both in the gas phase and on grain surfaces. However, the relative importance of these two chemical pathways is unclear. Comparison of the deuteration fraction of H2CO with respect to that of N2H+, NH3 and CH3OH can help us to understand its formation processes and time-scales. With the new SEPIA Band 5 receiver on APEX, we have observed the J=3-2 rotational lines of HDCO and D2CO at 193 GHz and 175 GHz toward three massive star forming regions hosting objects at different evolutionary stages: two High-mass Starless Cores (HMSC), two High-mass Protostellar Objects (HMPOs), and one Ultracompact HII region (UCHII). By using previously obtained H2CO J=3-2 data, the deuteration fractions HDCO/H2CO and D2CO/HDCO are estimated. Our observations show that singly-deuterated H2CO is detected toward all sources and that the deuteration fraction of H2CO increases from the HMSC to the HMPO phase and then sharply decreases in the latest evolutionary stage (UCHII). The doubly-deuterated form of H2CO is detected only in the earlier evolutionary stages with D2CO/H2CO showing a pattern that is qualitatively consistent with that of HDCO/H2CO, within current uncertainties. Our initial results show that H2CO may display a similar D$_{frac}$ pattern as that of CH3OH in massive young stellar objects. This finding suggests that solid state reactions dominate its formation.
We have investigated the process of $Lambda_bto Lambda Dbar{D}$, by taking into account the contributions from the $s$-wave $Dbar{D}$ interaction within the coupled-channel unitary approach, and the intermediate $psi(3770)$ resonance. In addition to the peak of the $psi(3770)$, an enhancement near the $Dbar{D}$ mass threshold is found in the $Dbar{D}$ invariant mass distributions, which should be the reflection of the $Dbar{D}$ bound state. We would like to encourage our experimental colleagues to measure the $Dbar{D}$ invariant mass distribution of the $Lambda_bto Lambda Dbar{D}$ process, which is crucial to search for the $Dbar{D}$ bound state and to understand the heavy-hadron heavy-hadron interactions.
Observationally, the interstellar gas-phase abundance of deuterium (D) is considerably depleted and the missing D atoms are often postulated to have been locked up into carbonaceous solids and polycyclic aromatic hydrocarbon (PAH) molecules. An accurate knowledge of the fractional amount of D (relative to H) tied up in carbon dust and PAHs has important cosmological implications since D originated exclusively from the Big Bang and the present-day D abundance, after accounting for the astration it has experienced during the Galactic evolution, provides essential clues to the primordial nucleosynthesis and the cosmological parameters. To quantitatively explore the extent to which PAHs could possibly accommodate the observed D depletion, we have previously quantum-chemically computed the infrared vibrational spectra of mono-deuterated PAHs and derived the mean intrinsic band strengths of the 3.3 $mu$m C--H stretch (A$_{3.3}$) and the 4.4 $mu$m C--D stretch (A$_{4.4}$). Here we extend our previous work to multi-deuterated PAH species of different deuterations, sizes and structures. We find that both the intrinsic band strengths A$_{3.3}$ and A$_{4.4}$ and their ratios A$_{4.4}$/A$_{3.3}$ not only show little variations among PAHs of different deuterations, sizes and structures, they are also closely similar to that of mono-deuterated PAHs. Therefore, a PAH deuteration level (i.e., the fraction of peripheral atoms attached to C atoms in the form of D) of ~2.4% previously estimated from the observed 4.4 $mu$m to 3.3 $mu$m band ratio based on the A$_{4.4}$/A$_{3.3}$ ratio of mono-deuterated PAHs is robust.
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