共查询到20条相似文献,搜索用时 916 毫秒
1.
A. V. Okotrub L. G. Bulusheva A. G. Kudashov V. V. Belavin D. V. Vyalikh S. L. Molodtsov 《Applied Physics A: Materials Science & Processing》2009,94(3):437-443
Arrays of vertically aligned nitrogen-doped carbon (CN
x
) nanotubes have been synthesized by decomposition of aerosol mixture of acetonitrile and ferrocene at 850°C. Nitrogen concentration
in the outer shells of the CN
x
nanotubes was found from X-ray photoelectron spectroscopy (XPS) data to reach ∼6%. The XPS N 1s spectra and N 1s near-edge X-ray absorption fine structure (NEXAFS) spectra identified three chemical forms of nitrogen in the CN
x
nanotube arrays: pyridine-like, graphitic, and molecular nitrogen. The π
* resonance of molecular nitrogen showed clear polarization dependence that indicates predominant orientation of N2 molecules along the nanotubes axis. The estimated range of the polar angle distribution of the N2 molecules orientation in the CN
x
nanotube array amounts to 15°. 相似文献
2.
Zhi-Gang Wang 《The European Physical Journal C - Particles and Fields》2008,56(2):181-187
In this article, we calculate the strong coupling constants gBs0Bsη and gBs1B*sη with the light-cone QCD sum rules. Then we take into account the small η–π0 transition matrix according to Dashen’s theorem, and we obtain the small decay widths for the isospin violation processes
Bs0→Bsη→Bsπ0 and Bs1→Bs
*η→Bs
*π0. We can search the strange-bottomed (0+,1+) mesons Bs0 and Bs1 in the invariant Bsπ0 and B*
sπ0 mass distributions, respectively.
PACS 12.38.Lg; 13.25.Hw; 14.40.Nd 相似文献
3.
P. Dietrich F. Michalik R. Schmidt C. Gahl G. Mao M. Breusing M. B. Raschke B. Priewisch T. Elsässer R. Mendelsohn M. Weinelt K. Rück-Braun 《Applied Physics A: Materials Science & Processing》2008,93(2):285-292
A mild and efficient procedure has been developed to obtain covalently attached self-assembled monolayers (SAMs) on Si(111)
with photochromic azobenzene head-groups. Starting from neat or diluted carboxylic acid functionalized monolayers on-chip
coupling reactions were applied to attach hydroxyl-functionalized azobenzene units to the SAMs by ester bond formation. The
modified surfaces were characterized by high-resolution X-ray photoelectron spectroscopy (XPS), transmission Fourier transform
infrared spectroscopy (FT-IR), and contact angle measurements. Reversible cis
↔
trans isomerizations of photoswitchable SAMs were monitored by wettability measurements.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users.
Dedicated with respect and compliments to Professor Helmut Schwarz on the occasion of his 65th birthday. 相似文献
4.
X.-H. Guo Gang Lü Z.-H. Zhang 《The European Physical Journal C - Particles and Fields》2008,58(2):223-244
In the framework of factorization we study direct CP violation in the decays of bottom hadrons containing a strange quark or a charm quark, H
b
→f
ρ
0(ω)→f
π
+
π
− (H
b
is the bottom hadron and f is the product hadron) including the effect of ρ–ω mixing. We find that the CP violating asymmetry can be enhanced greatly via the ρ–ω mixing mechanism when the invariant mass of the π
+
π
− pair is in the vicinity of the ω resonance. For the processes associated with b→d transitions, e.g.
,
, B
c
−→D
−
π
+
π
−, B
c
−→D
*−
π
+
π
−, Ξ
b
0→Λ
π
+
π
−, and Ω
b
−→Ξ
−
π
+
π
−, the maximum CP violating asymmetries can reach about −84%, while for the processes associated with b→s transitions, e.g.
,
, B
c
−→D
s
−
π
+
π
−, B
c
−→D
s
*−
π
+
π
−, Ξ
b
−→Ξ
−
π
+
π
−, and Ω
b
−→Ω
−
π
+
π
−, the CP violating asymmetries can be enhanced to about 95%. Furthermore, taking ρ–ω mixing into account we calculate the b-hadron decay branching ratios. We also discuss the possibility to observe the predicted CP violating asymmetries at the LHC. 相似文献
5.
N. A. Nemkovich H. Detert V. Schmitt Yu. V. Kruchenok 《Journal of Applied Spectroscopy》2012,79(3):353-359
Absorption and fluorescence spectra of octupolar centrosymmetric oligophenylenevinylene dyes (E,E)-bis[2-(4-hexyloxyphenyl)ethenyl]-(E,E)-3,6-bis-[2-(4-N,N-dipropylaminophenyl)ethenyl]pyrazine and (E,E,E,E)-2,3,5,6- tetra-[2-(4-hexyloxyphenyl)ethenyl]pyrazine were measured in various solvents. An electro-optical absorption method was used to determine their dipole moments as μ g = 6.1∙10–30 and 3.4∙10–30 C∙m in the equilibrium ground state and the increased values ∆ a μ = 11.9∙10–30 and 8.2∙10–30 C∙m upon excitation into a Franck–Condon state. Quantum-chemical calculations showed that the molecules had non-planar configurations. The π,π-conjugated system was localized on the most planar part of the molecule that was responsible for light absorption in the range 300–450 nm due to a change in the geometry of the molecules in the ground state. Localized excitation of the molecules caused their dipole moments ∆ a μ to change significantly. 相似文献
6.
Two-and three-body decays of γ(5S) into BB, BB*, B*B*, B
s
B
s
, B
s
B
s
*, and BB*π, B*B*π are evaluated using the theory developed earlier for dipion-bottomonium transitions. The theory contains only two parameters—vertex
masses M
br
and M
ω—known from the dipion spectra and width. Predicted values of Γtot(5S) and six partial widths Γ
k
(5S), k = BB, BB*, ... are in agreement with the experiment. The decay widths Γ5S
(πBB*) and Γ5S
(πB*B*) are also calculated and found to be on the order of 10 keV.
The text was submitted by the authors in English. 相似文献
7.
S. Abd El-Bary S. Abd El-Samad R. Bilger K. -Th. Brinkmann H. Clement M. Dietrich E. Doroshkevich S. Dshemuchadse K. Ehrhardt A. Erhardt W. Eyrich A. Filippi H. Freiesleben M. Fritsch R. Geyer A. Gillitzer C. Hanhart J. Hauffe K. Haug D. Hesselbarth R. Jaekel B. Jakob L. Karsch K. Kilian H. Koch J. Kress E. Kuhlmann S. Marcello S. Marwinski R. Meier K. Möller H. P. Morsch L. Naumann J. Ritman E. Roderburg P. Schönmeier M. Schulte-Wissermann W. Schroeder M. Steinke F. Stinzing G. Y. Sun J. Wächter G. J. Wagner M. Wagner U. Weidlich A. Wilms P. Wintz S. Wirth G. Zhang P. Zupranski 《The European Physical Journal A - Hadrons and Nuclei》2008,37(3):267-277
The two-pion production reaction pp → ppπ+π− was measured with a polarized proton beam at T
p
≈ 750 and 800MeV using the short version of the COSY-TOF spectrometer. The implementation of a delayed-pulse technique for
Quirl and central calorimeter provided positive π+ identification in addition to the standard particle identification, energy determination as well as time-of-flight and angle
measurements. Thus all four-momenta of the emerging particles could be determined with 1–4 overconstraints. Total and differential
cross-sections as well as angular distributions of the vector analyzing power have been obtained. They are compared to previous
data and theoretical calculations. In contrast to predictions we find significant analyzing-power values up to A
y
= 0.3. The data taken in the energy region of the excitation of the Roper resonance confirm that its dominant ππ decay channel
is N
* → Nσ. 相似文献
8.
C.M. Marian F. Schneider M. Kleinschmidt J. Tatchen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(3):357-367
Electronic spectra of uracil in its diketo (lactam) form and five enol (lactim) tautomeric forms have been investigated by
means of combined density functional and configuration interaction methods. We have simulated the effects of hydrogen bonding
with a protic solvent by recomputing the spectrum of uracil in the presence of two, four, or six water molecules. Geometries
of the electronic ground state and several low-lying excited states have been optimized. Spin-orbit coupling has been determined
for correlated wavefunctions employing a non-empirical spin-orbit mean-field approach. In accord with experiment, we find
the diketo tautomer to be the most stable one. The calculations confirm that the first absorption band arises from the 1( π↦π*) S
0↦S
2 excitation. The experimentally observed vibrational structure in this band originates from a breathing mode of the six ring.
Complexation with water molecules is seen to cause a significant blue shift of n↦π* excitations while leaving π↦π* excitations nearly uninfluenced. Computed radiative lifetimes are presented for the experimentally known weak phosphorescence
from the π↦π* excited T1 state. Among the uracil lactim tautomers, one is particularly interesting from a spectroscopic point of view. In this tautomer,
the π↦π* excitation gives rise to the S1 state.
Received 18 February 2002 / Received in final form 5 June 2002 Published online 13 September 2002 相似文献
9.
We demonstrate n-type doping of pentacene with the powerful reducing molecule decamethylcobaltocene (CoCp2*). Characterization of pentacene films deposited in a background pressure of CoCp2* by X-ray photoemission spectroscopy and Rutherford backscattering confirm that the concentration of incorporated donor molecules
can be controlled to a level as high as 1%. Ultraviolet photoemission spectroscopy show Fermi level (E
F) shifts toward unoccupied pentacene states, indicative of an increase in the electron concentration. A 1% donor incorporation
level brings E
F to 0.6 eV below the pentacene lowest unoccupied molecular orbital. The corresponding electron density of ∼1018 cm−3 is confirmed by capacitance–voltage measurements on a metal–pentacene–oxide–silicon structure. The demonstration of n-doping
suggests applications of CoCp2* to pentacene contacts or channel regions of pentacene OTFTs. 相似文献
10.
A. Gutiérrez J. Díaz M. F. López 《Applied Physics A: Materials Science & Processing》1995,61(2):111-114
Amorphous carbon (a-C) films obtained by pulsed-laser ablation of graphite have been investigated by X-ray Absorption Spectroscopy (XAS). The onset of 1s
* transitions in the films lies in the gap between the
* and
* bands in graphite and very close to the absorption edge of diamond, indicating a high content ofsp
3 hybridization. A sharp feature at this onset is observed and assigned to a core exciton insp
3-hybridized disordered C atoms. Its shift of 0.5 eV with respect to the core exciton in diamond is probably due to a higher localization of the excited electron induced by disorder. A small peak coming from C–H bonds at the surface is observed and its intensity inereases with the amount ofsp
3-hybridized atoms in the sample. This can be easily explained by associating a higher amount of dangling bonds at the surface to a highersp
3 content. Polarization-dependent XAS measurements show that the angular distribution of these C–H bonds has a mean value close to the normal to the surface. 相似文献
11.
Shi-Lin Zhu 《The European Physical Journal A - Hadrons and Nuclei》1999,4(3):277-281
The light cone QCD sum rules are derived for the K
*
Kπ coupling g
K
*
Kπ and the ρππ coupling g
ρππ. The contribution from the excited states and the continuum is subtracted cleanly through the double Borel transform with
respect to the two external momenta, p
1
2, p
2
2= (p−q)2. Our result g
K
*
Kπ= (8.7 ± 0.5) and g
ρππ= (11.5 ± 0.8) is in good agreement with the experimental value.
Received: 31 July 1998 / Revised version: 20 November 1998 相似文献
12.
A.L. Sobolewski W. Domcke 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(3):369-374
Minimum-energy reaction paths and corresponding potential-energy profiles have been computed for the lowest excited states of the amino form of 9H-adenine. Complete-active- space self-consistent-field (CASSCF) and density functional theory (DFT) methods have been employed. The potential-energy function of the lowest 1πσ* state, nominally a 3s Rydberg state, is found to be dissociative with respect to the stretching of the NH bond length of the azine group. The 1πσ* potential-energy function intersects not only those of the 1ππ* and 1 nπ* excited states, but also that of the electronic ground state. The 1ππ*- 1πσ* and 1πσ*-S0 intersections are converted into conical intersections when the out-of-plane motion of the active hydrogen atom is taken into account. It is argued that the predissociation of the 1ππ* and 1 nπ* states by the 1πσ* state and the conical intersection of the 1πσ* state with the S0 state provide the mechanism for the ultrafast radiationless deactivation of the excited singlet states of adenine. 相似文献
13.
A systematic study of the chemical bonding in hydrogenated amorphous germanium–carbon (a-Ge1-xCx:H)alloys using X-ray photoelectron spectroscopy (XPS) is presented. The films, with carbon content ranging from 0 at. % to
100 at. %, were prepared by the rf co-sputtering technique. Raman spectroscopy was used to investigate the carbon hybridization.
Rutherford backscattering spectroscopy (RBS) and XPS were used to determine the film stoichiometry. The Ge 3d and C 1s core
levels were used for investigating the bonding properties of germanium and carbon atoms, respectively. The relative concentrations
of C–Ge, C–C, and C–H bonds were calculated using the intensities of the chemically shifted C 1s components. It was observed
that the carbon atoms enter the germanium network with different hybridization, which depends on the carbon concentration.
For concentrations lower than 20 at. %, the carbon atoms are preferentially sp3 hybridized, and approximately randomly distributed. As the carbon content increases the concentration of sp2 sites also increases and the films are more graphitic-like.
Received: 4 May 1999 / Accepted: 24 November 1999 / Published online: 24 March 2000 相似文献
14.
R. Arnaldi K. Banicz K. Borer J. Castor B. Chaurand W. Chen C. Cicalò A. Colla P. Cortese S. Damjanovic A. David A. de Falco A. Devaux L. Ducroux H. En’yo J. Fargeix A. Ferretti M. Floris A. F?rster P. Force N. Guettet A. Guichard H. Gulkanian J. M. Heuser M. Keil L. Kluberg Z. Li C. Louren?o J. Lozano F. Manso P. Martins A. Masoni A. Neves H. Ohnishi C. Oppedisano P. Parracho P. Pillot T. Poghosyan G. Puddu E. Radermacher P. Ramalhete P. Rosinsky E. Scomparin J. Seixas S. Serci R. Shahoyan P. Sonderegger H. J. Specht R. Tieulent G. Usai R. Veenhof H. K. W?hri 《The European Physical Journal C - Particles and Fields》2009,61(4):711-720
The NA60 experiment at the CERN SPS has measured muon pairs with unprecedented precision in 158 A GeV In–In collisions. A strong excess of pairs above the known sources is observed in the whole mass region 0.2<M<2.6 GeV. The mass spectrum for M<1 GeV is consistent with a dominant contribution from π
+
π
−→ρ→μ
+
μ
− annihilation. The associated ρ spectral function shows a strong broadening, but essentially no shift in mass. For M>1 GeV, the excess is found to be prompt, not due to enhanced charm production, with pronounced differences to Drell–Yan pairs.
The slope parameter T
eff associated with the transverse momentum spectra rises with mass up to the ρ, followed by a sudden decline above. The rise for M<1 GeV is consistent with radial flow of a hadronic emission source. The seeming absence of significant flow for M>1 GeV and its relation to parton–hadron duality is discussed in detail, suggesting a dominantly partonic emission source
in this region. A comparison of the data to the present status of theoretical modeling is also contained. The accumulated
empirical evidence, including also a Planck-like shape of the mass spectra at low p
T
and the lack of polarization, is consistent with a global interpretation of the excess dimuons as thermal radiation. We conclude
with first results on ω in-medium effects. 相似文献
15.
P. Zh. Aslanyan 《Physics of Particles and Nuclei》2009,40(4):525-557
Exotic strange multibaryon states have been observed in the effective mass spectra of: Λπ±, Λπ+π−, Λp, Λpp, Λπp, ΛΛ and ΛK
s
0, K
s
0
p, K
s
0π± subsystems. The measured Λ/π+ ratio for average multiplicities from the pC reaction is equal to (5.3 ± 0.8) × 10−2, and it is approximately two times larger than the Λ/π+ ratio simulated by the FRITIOF model and than that of experimental pp reactions at the same energy. The observed wellknown resonances Σ*+ (1385) and K*± (892) from PDG are good tests of this method. The mean value of the mass for the Σ*−(1385) resonance is shifted to 1370 MeV/c
2 and the width is two times larger than the same value from PDG. Such kind of behavior for the width and invariant mass of
Σ*− (1385) resonance is interpreted as an extensive contribution from stopped Ξ− → Λπ− and medium effect. There is enhancement of the production contribution for all observed hyperons. A few events were registered
by hypothesis of light H
0 and heavy H
0, + dihyperons. Dihyperons were observed by weak decay channels: (Σ−
p), (Λpπ−), (Λpπ0), and (K
−
pp).
The text was submitted by the author in English. 相似文献
16.
M. Ramm M. Ata T. Gross W. Unger 《Applied Physics A: Materials Science & Processing》2000,70(4):387-390
We report core-level and valence-band X-ray photoelectron spectroscopy (XPS) and carbon [
]K near-edge X-ray-absorptionfine structure spectroscopy (NEXAFS) results of plasma-polymerized C60. In comparison with evaporated C60 the C 1s peak is broader and asymmetric for the C60 polymer and its shake-up satellites diminished. Furthermore, the features of the valence-band as well as the features of
the π* antibonding orbitals of the C60 polymer are broader and reduced in intensity. Changes in the electronic structure are attributed to the polymerization of
C60, the post-plasma functionalization of the surface by oxygen after exposure to atmosphere, and the occurrence of amorphous
carbon.
Received: 28 May 1999 / Accepted: 31 August 1999 / Published online: 8 March 2000 相似文献
17.
F.?Roth A.?K?nig R.?Kraus M.?Grobosch T.?Kroll M.?Knupfer 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,74(3):339-344
We have studied the electronic structure of iron phthalocyanine (FePc) films at low temperature using electron energy-loss
spectroscopy. The electronic excitation spectrum of FePc is rather complex and comprises both π-π* transitions of the phthalocyanine ligand and transitions that involve the Fe 3d orbitals. The C 1s core excitations provide
so far unidentified information on the molecular orbitals. They demonstrate that the Fe 3d orbital with eg symmetry is energetically located in between the highest occupied and the lowest unoccupied ligand state and that it is not
fully occupied. 相似文献
18.
M. A. Algatti R. P. Mota R. Y. Honda M. E. Kayama K. G. Kostov R. S. Fernandes T. C.A.M. Azevedo N. C. Cruz 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):325-328
This paper deals with plasma polymerization processes of diethylene glycol dimethyl ether. Plasmas were produced at 150 mtorr
in the range of 10 W to 40 W of RF power. Films were grown on silicon and quartz substrates. Molecular structure of plasma
polymerized films and their optical properties were analyzed by Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible
spectroscopy. The IR spectra show C–H stretching at 3000–2900 cm-1, C=O stretching at 1730–1650 cm-1, C–H bending at 1440–1380 cm-1, C–O and C–O–C stretching at 1200–1000 cm-1. The concentrations of C–H, C–O and C–O–C were investigated for different values of RF power. It can be seen that the C–H
concentration increases from 0.55 to 1.0 au (arbitrary unit) with the increase of RF power from 10 to 40 W. The concentration
of C–O and C–O–C decreases from 1.0 to 0.5 au in the same range of RF power. The refraction index increased from 1.47 to 1.61
with the increase of RF power. The optical gap calculated from absorption coefficient decreased from 5.15 to 3.35 eV with
the increase of power. Due to its optical and hydrophilic characteristics these films can be applied, for instance, as glass
lens coatings for ophthalmic applications. 相似文献
19.
BES II data for J/Ψ↦K
*(890)Kπ reveal a strong κ peak in the Kπ S-wave near threshold. Both magnitude and phase are determined in slices of Kπ mass by interferences with strong K
0(1430), K
1(1270) and K
1(1400) signals. The phase variation with mass agrees within errors with LASS data for Kπ elastic scattering. A combined fit is presented to both BES and LASS data. The fit uses a Breit-Wigner amplitude with an
s-dependent width containing an Adler zero. The κ pole is at (760±20(stat)±40(syst)) - i(420±45(stat)±60(syst)) MeV. The S-wave I = 0 scattering length a
0 = 0.23±0.04 m
π
-1 is close to the prediction 0.19±0.02 m
π
-1 of Chiral Perturbation Theory at O(p
4).
An erratum to this article can be found at . 相似文献
20.
《The European Physical Journal A - Hadrons and Nuclei》2008,35(3):333-342
The exclusive reactions γp → K
*0Σ+(1189) and γp → K
0π0Σ+(1189) , leading to the p 4π0 final state, have been measured with a tagged photon beam for incident energies from threshold up to 2.5GeV. The experiment
has been performed at the tagged photon facility of the ELSA accelerator (Bonn). The Crystal Barrel and TAPS detectors were
combined to a photon detector system of almost 4π geometrical acceptance. Differential and total cross-sections are reported.
At energies close to the threshold, a flat angular distribution has been observed for the reaction γp → K
0π0Σ+ suggesting dominant s -channel production. Σ*(1385) and higher-lying hyperon states have been observed. An enhancement in the forward direction in the angular distributions
of the reaction γp → K
*0Σ+ indicates a t -channel exchange contribution to the reaction mechanism. The experimental data are in reasonable agreement with recent theoretical
predictions. 相似文献