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1.
The ultraviolet (UV) photodissociation of jet-cooled 1-pentyl radical is investigated in the wavelength region of 236-254 nm using the high-n Rydberg-atom time-of-flight (HRTOF) technique. The H-atom photofragment yield spectrum of the 1-pentyl radical shows a broad UV absorption feature peaking near 245 nm, similar to the 2pz→3s absorption bands of ethyl and n-propyl. The center-of-mass translational energy distribution, P(ET), of the H+C5H10 product channel is bimodal, with a slow peak at~5 kcal/mol and a fast peak at~50 kcal/mol. The fraction of the average translational energy release in the total available energy, 〈fT〉, is 0.30, with those of the slow and fast components being 0.13 and 0.58, respectively. The slow component has an isotropic product angular distribution, while the fast component is anisotropic with an anisotropy parameter~0.4. The bimodal translational energy and angular distributions of the H+C5H10 products indicate two H-atom elimination channels in the photodissociation of 1-pentyl:(i) a direct, prompt dissociation from the electronic excited state and/or the repulsive part of the ground electronic state potential energy surface; and (ii) a unimolecular dissociation of internally hot radical in the ground electronic state after internal conversion from the electronic excited state. 相似文献
2.
A. A. Samokhvalov T. I. Arbuzova N. A. Viglin V. V. Osipov N. I. Solin S. V. Naumov V. G. Bamburov N. I. Lobachevskaya O. G. Reznitskikh 《Physics of the Solid State》1999,41(2):262-264
Mg1−x
CuxO solid solutions having an NaCl structure with 0⩽x⩽0.20 are synthesized and Cu-Mg1−x
CuxO structures are prepared for superconductivity studies. The magnetic susceptibility χ, electron paramagnetic resonance (EPR), and electrical conductivity of the solid solutions are studied at temperatures of
5–550 K. It is shown that χ
−1(T) obeys the Curie-Weiss law with a paramagnetic Curie temperature Θ close to zero and an effective magnetic moment μ
eff=1.9 μ
B, close to the 1.73 μ
B of a Cu2+ ion with spin S=1/2. The width ΔH of the EPR line depends weakly on temperature and increases as x is raised. The volume narrowing of the EPR linewidth ΔH is used to estimate the exchange interaction parameter, 3×10−4 eV. The g-factor is close to 2 and is temperature independent. The electrical conductivity of Mg1−x
CuxO at T=300 K is ≈10−11–10−12 Ω−1 cm−1 for x=0 and increases to 10−5–10−6 Ω−1 cm−1 for x=0.15–0.20. The conductivity is p-type. Magnetic shielding is observed in Cu-Mg1−x
CuxO structures with x=0.15 and 0.20. The possible connection of this phenomenon with interference superconductivity in the contact layer of the
structure is discussed.
Fiz. Tverd. Tela (St. Petersburg) 41, 293–296 (February 1999) 相似文献
3.
S.V. Golovkin A.P. Kozhevnikov V.P. Kubarovsky V.F. Kurshetsov L.G. Landsberg V.V. Molchanov V.A. Mukhin S.V. Petrenko V.A. Senko D.V. Vavilov V.A. Victorov V.Z. Kolganov G.S. Lomkatsi A.F. Nilov V.T. Smolyankin 《The European Physical Journal A - Hadrons and Nuclei》1999,5(4):409-416
New data for the diffractive reaction p+N→ [Σ0
K
+] +N at E
p= 70 GeV were obtained with partially upgraded SPHINX setup. The data are in a good agreement with the results of our previous
study of this reaction. In the mass spectrum M(Σ0
K
+) a structure at the threshold region with a mass ∼1810 MeV and a distinct X(2000) peak with M= 1989 ± 6 MeV and γ= 91 ± 20 MeV are observed. Unusual features of the massive X(2000) state (narrow decay width, anomalously
large branching ratio for the decay channel with strange particle emission) make it a serious candidate for cryptoexotic pentaquark
baryon with hidden strangeness |qqqsˉs>. We also present new results on the narrow threshold structure X(1810) with M= 1807 ± 7 MeV and γ= 62 ± 19 MeV which is produced in the region of very small P
2
T < 0.01 GeV2. The possibility of the Coulomb production mechanism for X(1810) is discussed.
Received: 28 April 1999 相似文献
4.
The occurrence of discontinuities in the energy spectrum of thes-wave Hamiltonian in three dimensionsH(μ, λ) =p
2/2 − 1/r + 2μr + 2λ
2
r
2 has been reported by us. In this communication we develop a unified understanding, based principally on the topography of
the energy surfaces, of the different discontinuities we reported earlier. These discontinuities do not in general occur wherever
the corresponding classical system would display catastrophic behaviour. 相似文献
5.
The φπ+π− production in pˉp annihilation at rest is strongly enhanced by a two step mechanism with intermediate KˉKππ states. The relative yield of the φ production due to the resonant final state interaction decreases with increasing total
energy of the pˉp system.
Received: 4 August 1997 相似文献
6.
S. Tresch P. Ackerbauer M. Augsburger W.H. Breunlich M. Cargnelli D. Chatellard J.-P. Egger T. von Egidy B. Gartner F.J. Hartmann R. Jacot-Guillarmod E. Jeannet R. King B. Lauss J. Marton M. Mühlbauer F. Mulhauser C. Petitjean C. Piller W. Prymas L.A. Schaller L. Schellenberg H. Schneuwly W. Schott Y.-A. Thalmann A. Werthmüller J. Zmeskal 《Hyperfine Interactions》1999,119(1-4):109-114
The transfer reaction of negative muons from muonic protium to 3 and 4 in binary and triple gas mixtures was studied. In the binary mixtures the transfer rates to the two helium isotopes were
determined from the time distribution of the 7-keV X-rays of the intermediate muonic molecule (pμHe)*. The experimental transfer rate to 4 is in good agreement with theoretical predictions, whereas the rate to 3 is a factor 2 to 3 smaller than the predicted ones. Radiative branching ratios of the (pμHe)8 molecular decay were obtained. Muon transfer from excited states of muonic protium gives the main contribution to the
total intensity of the μHe Lyman series in the binary mixtures. Values of q
1s
He
are determined.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
The cross-sections for the reactions of muonium (anti-muonium) production in the high-energy electron (positron) scattering
by nuclei e
-(e
+) + Z↦Z + M
0(ˉM) + μ-(μ+) are calculated in dependence on energy and polarization of the initial electron (positron) and polarization of the final
μ-(μ+)-meson. Since this is a coherent phenomenon the cross-sections are proportional to Z2. For Z ∼ 100, due to the factor Z2, the cross-sections are large enough to be measured at the energies available for the HERA Collider at DESY. The results
are discussed in connection with a test of CPT invariance.
Received: 24 September 2002 / Accepted: 12 March 2003 / Published online: 27 May 2003 相似文献
8.
V. S. Egorov E. P. Krasnoperov F. V. Lykov U. Zimmermann G. Solt C. Baines D. Herlach 《Physics of the Solid State》1998,40(3):482-484
We have observed diamagnetic domains (Condon domains) in a beryllium single crystal in magnetic fields H⩽3 T (H∥[0001]) at liquid-helium temperatures. The formation of the domain structure was determined according to magnetic-breakdown
quantum oscillations of the resistance thermoelectric power as well as according to the splitting of the resonance peak of
the free spin precession frequency of muons (μSR). The alternation of a uniform state (with one μSR peak) and a state with
domain structure (with two peaks) is consistent as regards the periodicity with the de Haas-van Alphen effect, the period
is ΔH≅78 Oe, and the range of existence of domains and the difference in their magnetizations are ΔB=4πΔM=B
2−B
1≅30 Oe.
Fiz. Tverd. Tela (St. Petersburg) 40, 524–526 (March 1998) 相似文献
9.
O. B. Gusev M. S. Bresler B. P. Zakharchenya A. N. Kuznetsov P. E. Pak E. I. Terukov K. D. Tséndin I. N. Yassievich 《Physics of the Solid State》1999,41(2):185-191
A study of the electroluminescence of erbium-doped, amorphous hydrogenated silicon, a-Si:H 〈Er〉, is reported. It has been found that the electroluminescence intensity at the wavelength λ=1.54 μm corresponding to the 4
I
13/2→4
I
15/2 intra-4f shell transition in Er passes through a maximum near room temperature. The unusual temperature and field dependences of the
electroluminescence indicate electric-field induced multi-phonon tunneling emission of electrons from deep centers. The electroluminescence
of Er3+ ions is due to their becoming excited as conduction-band electrons are captured by neutral dangling bonds (D
0 centers), which form when erbium is incorporated into the amorphous matrix. This Auger process transforms the center from
its neutral state, D
0, to a negatively charged state, D
−, and the energy released in the capture is transferred by Coulomb interaction into the erbium-ion 4f shell. The steady-state current through the electroluminescent structure is supported by the reverse process of multi-phonon
tunneling-electron emission from the D
− center to the conduction band. The proposed theoretical model is in a good agreement with experimental data.
Fiz. Tverd. Tela (St. Petersburg) 41, 210–217 (February 1999) 相似文献
10.
R. Feyerherm A. Amato A. Grayevsky F. N. Gygax N. Kaplan A. Schenck 《Zeitschrift für Physik B Condensed Matter》1995,99(1):3-13
Muon spin rotation measurements of the temperature dependence and the anisotropy of the μ+ Knight shift in single crystals of the crystal electric field singlet ground state system PrNi5 reveal pronounced deviations from a linear scaling of the Knight shift with the bulk magnetic susceptibility atT≤50 K. They are explained by a μ+ induced modification of the atomic susceptibility of neighboring Pr3+ ions. From the Knight shift anisotropy atT> 50 K it is determined that the implanted μ+ occupy a single intersitial site, namely the 6i site (0.5, 0, 0.21±0.02). Using this site information, good model fits to
the measured data are obtained assuming a μ+ induced perturbation of the crystal electric field at the Pr3+ ions next to the μ+. Apparently, the presence of the μ+ leads to a lowering of the local symmetry, causing a lifting of the degeneracy and a pronounced rearrangement of the low
lying crystal electric field levels for these ions. 相似文献
11.
We use different determinantal Hartree-Fock (HF) wave functions to calculate true variational upper bounds for the ground
state energy of N spin-half fermions in volume V
0, with mass m, electric charge zero, and magnetic moment μ, interacting through magnetic dipole-dipole interaction. We find that at high
densities when the average interparticle distance r
0 becomes small compared to the magnetic length r
m ≡ 2mμ2/ħ2, a ferromagnetic state with spheroidal occupation function n
↑(), involving quadrupolar deformation, gives a lower upper bound compared to the variational energy for the uniform paramagnetic
state or for the state with dipolar deformation. This system is unstable towards infinite density collapse, but we show explicitly
that a suitable short-range repulsive (hard core) interaction of strength U
0 and range a can stop this collapse. The existence of a stable equilibrium high density ferromagnetic state with spheroidal occupation
function is possible as long as the ratio of coupling constants Γcm ≡ (U
0
a
3/μ2) is not very small compared to 1.
相似文献
12.
G. Litsardakis D. Samaras A. Collomb J. P. Mignot 《Applied Physics A: Materials Science & Processing》1988,47(4):327-331
The Mn cation distribution in the seven sublattices of theW-type structure has been determined from high temperature neutron diffraction data of a SrMn2Fe16O27 powder sample. The Mn2+ ions enter the tetrahedral sites of blockS with a preference for site 4e. Mn3+ ions in small amounts are found in the octahedral sites, substituting for Fe3+, while 0.3 Fe2+ has been found in site 6g. The sample has the formula SrMn2.4Fe15.6O27. The crystal structure has been described in the non-centrosymmetric Pˉ62c space group, instead of the usual P63/mmc one. The magnetic structure, obtained from low temperature (4.2 K) data, is collinear, with the spins parallel to thec axis, according to the Gorter model. The magnetic moments of the sites give an experimental magnetization valueM
s=28.4(1.5) μB/f.u., in good agreement with magnetic measurements and the theoretical value. 相似文献
13.
Analytic expressions are obtained for vibrational transition moments of the first, second, and third orders using the eigenfunctions
in the second-order perturbation theory. These expressions can be used to solve the inverse electrooptical problem for the
12C16O2 molecule. The resonance interactions were taken into account by solving secular equations. The mixing coefficients for the
eigenfunctions were calculated with an accuracy of 0.1%. The experimental data on purely vibrational transition moments 〈μ〉2 used in the solution were obtained by averaging the data available in the literature with the weights that are inversely
proportional to the error, resulting in mean-square deviations of (0.1–10)%. Five parameters of the dipole moment of the Σ
u
symmetry were calculated using 29 values of the transition moments; five parameters of the πu symmetry were calculated using 27 values of the transition moments. The accuracy of the solution of the inverse problem is
characterized by the quantity Q=[Σ(δμ
i
(theor)
/δμ
i
(exp)
)2/(n-m)]1/2, where δμ
i
(theor)
is the deviation of calculations from the experiment, δμ
(exp)
i
is the experimental error, n is the number of the experimental data used, and m is the number of parameters smaller than unity.
__________
Translated from Optika i Spektroskopiya, Vol. 88, No. 5, 2000, pp. pp719–732.
Original Russian Text Copyright ? 2000 by Kolomiĭtsova, Lyaptsev, Shchepkin. 相似文献
14.
B. Gartner P. Ackerbauer M. Augsburger W.H. Breunlich M. Cargnelli D. Chatellard J.-P. Egger T. von Egidy F.J. Hartmann R. Jacot-Guillarmod E. Jeannet P. Kammel R.C. King A. Kosak B. Lauss J. Marton M. Mühlbauer F. Mulhauser C. Petitjean C. Piller W. Prymas L.A. Schaller L. Schellenberg H. Schneuwly W. Schott Y.A. Thalmann S. Tresch A. Werthmüller J. Zmeskal 《Hyperfine Interactions》1999,119(1-4):103-108
The energy and time distributions of the decay X-rays of excited, metastable, molecular (dμHe)*-resonances were measured. The comparison of the observed energy spectra with calculated ones suggests that decay from
the rotational state J = 1 dominates at the investigated conditions. The muon transfer rates from ground state deuterium to the helium isotopes
3He and 4He at low temperatures were determined from the time distributions of these spectra. Additionally, the temperature dependence
of the muon transfer rate was clearly established in deuterium / 4He mixtures.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
15.
E.G. Drukarev M.G. Ryskin V.A. Sadovnikova 《The European Physical Journal A - Hadrons and Nuclei》1999,4(2):171-186
We calculate the contribution of pions to the $\bar qq$-expectation value κ(ρ) =<M|ˉq
q|M> in symmetric nuclear matter. We employ exact pion propagator renormalized by nucleon-hole and isobar-hole excitations. Conventional
straightforward calculation leads to the “pion condensation” at unrealistically small values of densities, causing even earlier
restoration of chiral symmetry. This requires a self-consistent approach, consisting in using the models, which include direct
dependence of in-medium mass values on κ(ρ), e.g. the Nambu–Jona-Lasinio–model. We show, that in the self-consistent approach
the ρ-dependence of the condensate is described by a smooth curve. The “pion condensate” point is removed to much higher values
of density. The chiral restoration does not take place at least while ρ < 2.8ρ0 with ρ0 being the saturation value. Validity of our approach is limited by possible accumulation of heavier baryons (delta isobars)
in the ground state of nuclear matter. For the value of effective nucleon mass at the saturation density we found m
*(ρ0) = 0.6m, consistent with nowadays results of other authors.
Received: 8 October 1998 相似文献
16.
Using a pulsed capilary discharge through helium as a light source fluorescence within the Lyman bands (transitionX
1 ∑
g
+
→B
1 ∑
u
+
of molecular hydrogen and deuterium has been investigated. Selecting a narrow spectral range (width ≈ 8 ?) from the continuum
radiation with a spectrometer, lines in the wavelength range from 1060 ? to 1110 ? have been excited having a vibrational
quantum number υ″=0 in the lower state, and ≦υ′≦4 in the upper state. The fluorescence intensity has been measured as a function
of υ′ and of the hydrogen density. Agreement with calculations has been found to be within ±30%. The method at present allows
the determination of densities between 1010 and 1015 molecules per cm3 with a temporal resolution of 1μs and with a spacial resolution of 0.1 cm3 相似文献
17.
The photoinduced optical absorption α of doped yttrium iron garnets (YIG) is investigated. It is found that the optical absorption
α at a wavelength of 1.1 μm depends on the wavelength of irradiating light in the range 0.6–1.9 μm. It is demonstrated that,
in the Y3Fe5O12 crystal with an acceptor Ba impurity, the photoinduced increase in α is due to the formation of Fe4+ ions in octahedral sites. The charge transfer occurs through photoexcitation of the 6
A
1g
(6
S) → 4
T
1g
(4
G) and 6
A
1g
(6
S) → 4
T
2g
(4
G) transitions of octahedral Fe3+ ions. In the crystal with a donor Si impurity, the increase in α is caused by the formation of Fe2+ ions upon photoionization of silicon.
__________
Translated from Fizika Tverdogo Tela, Vol. 43, No. 7, 2001, pp. 1233–1235.
Original Russian Text Copyright ? 2001 by Doroshenko, Nadezhdin. 相似文献
18.
The resonance characteristics (inhomogeneous FMR linewidth ΔH) in highly dispersed (d=0.1–3 μm) powders of crystalline and amorphous Co-P alloys are investigated as a function of the composition, particle size, and
atomic structure. It is established that ΔH for powders of amorphous Co-P alloys is two to three times larger than ΔH for crystalline Co-P powders. According to the investigations performed, this is caused by thermodynamically stimulated segregation
of nonmagnetic Co2P inclusions, apparently an effective relaxation channel, in the amorphous state of Co-P powders.
Fiz. Tverd. Tela (St. Petersburg) 41, 464–467 (March 1999) 相似文献
19.
The electrode reaction was examined on ceria coated YSZ by a platinum point electrode in H2-H2O atmosphere at 973 K- 1173 K. The thickness of the ceria coating layer was altered from 0 to 2.5 μm, fabricated by a laser
ablation and by a vacuum vapor deposition method on YSZ single crystals. The electrode / electrolyte interface conductivity
increased with 1/4 powers ofp(H2) andp(H2O) on both ceria coated and non-coated YSZ. The interface conductivity was significantly improved on a thicker ceria coating
surface than 1 μm. The effective electrode reaction radius also increased in a thick ceria coating. The18O/16O exchange experiment at low oxygen partial pressure revealed that the oxygen surface exchange rate of ceria is not high compared
with that of YSZ. It can be concluded that the bulk ionic conduction of ceria makes a more effective contribution to the electrode
reaction than the surface catalytic activity in H2-H2O atmosphere.
Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997 相似文献
20.
R. A. Babunts V. A. Vetrov I. V. Il’in E. N. Mokhov N. G. Romanov V. A. Khramtsov P. G. Baranov 《Physics of the Solid State》2000,42(5):829-835
The infrared luminescence of Er3+ ions has been studied in bulk crystals of silicon carbide 6H-SiC doped with erbium in the process of their growth. The erbium centers of different symmetry in the crystals are revealed
by the EPR technique. A number of intense luminescence bands of erbium ions are observed at a wavelength of about 1.54 μm.
The luminescence can be excited by the light with quantum energies above and below the band gap of SiC. It is found that the
luminescence exhibits unusual temperature behavior: as the temperature increases, the luminescence intensity abruptly rises
starting with 77 K, passes through a maximum at ∼240 K, and, in the vicinity of ∼400 K, decreases down to the values observed
at 77 K. The activation energies for the flare-up and quenching of the Er3+ luminescence are estimated at E
A
≈130 and ≈350 meV, respectively. The mechanisms of the flare-up and quenching of the Er3+ luminescence in SiC are discussed.
__________
Translated from Fizika Tverdogo Tela, Vol. 42, No. 5, 2000, pp. 809–815.
Original Russian Text Copyright ? 2000 by Babunts, Vetrov, Il’in, Mokhov, Romanov, Khramtsov, Baranov. 相似文献