共查询到20条相似文献,搜索用时 15 毫秒
1.
N. A. Borisevich A. P. Lugovskii V. A. Povedailo E. E. Tselesh D. L. Yakovlev 《Journal of Applied Spectroscopy》2010,77(3):343-348
Conformations of He-jet-cooled trimethyl[(3-indole)ethoxy]silane (TIES) have been studied using a laser spectroscopy technique
in combination with quantum-chemical computations. Six probable conformers of the molecule were computed, of which only two
conformations were observed. Based on an analysis of fluorescence excitation spectra, fluorescence spectra, shapes of rotational
band contours at the electronic S0–S1 transition of TIES, and theoretical computations, the above conformers were assigned to steric structures. Twisted structures
have the lowest energy due to intramolecular hydrogen bonds C - H ?O < CSi C - H \cdots O <_C^{Si} between hydrogen atoms of methyl groups and an oxygen atom and C–H···π between H and the π-electron cloud of the indole ring. 相似文献
2.
O. V. Sizova V. I. Baranovskii A. I. Panin N. V. Ivanova 《Foundations of Physics Letters》2002,15(1):471-479
The dynamics of the intramolecular electron transfer from Ru(II) to Ru(III) in binuclear mixed-valence complexes [NH3)5Ru -L-Ru(NH3)5]5+
(L = N2, pyz, bipy, pym, bpa) is analyzed by the semiempirical CINDO + CI method.
Translated from ZhurnalStruktumoi Khimii, Vol. 39, No. 4, pp. 579–590, July–August, 1998. 相似文献
3.
C. Piliego F. Cordella D. Jarzab S. Lu Z. Chen A. Facchetti M. A. Loi 《Applied Physics A: Materials Science & Processing》2009,95(1):303-308
In this letter we compare the transistor performances of two solution-processed perylene derivatives: N,N′-bis (n-octyl)- dicyanoperylene-3,4:9,10-bis(dicarboximide) (PDI8-CN2) and N,N′-1H,1H-perfluorobutyl dicyanoperylenediimide (PDIF-CN2). Perylenediimide nitrogen functionalization with perfluoroalkyl vs. alkyl chains improves the electron mobility of solution-processed
organic field effect transistors (OFETs) by one order of magnitude. Time resolved spectroscopy allows attributing this increment
to a higher degree of co-facial arrangement of the fluorinated molecules. This supramolecular arrangement enhances the π–π overlap leading to more efficient electron transport. 相似文献
4.
The title compound, C26H24N2O6S, (I), crystallizes in the monoclinic space group, P21/c, with cell parameters a = 16.248(1), b = 7.927(1), c = 19.371(4) ?, β = 105.295(2)°, Z = 4. The central pyrimidine ring in the compound (I) is significantly puckered, assuming a screw-boat conformation. The C11–C16 benzene ring stands vertical while thiazole and
C18–C23 benzene rings are coplanar to the mean plane of pyrimidine ring having dihedral angles of 87.48(12), 3.63(11) and
0.94(12)°, respectively. In the absence of potential hydrogen bonding interaction, the crystal packing is influenced by intramolecular
C-H…S interaction and intermolecular C-H…π interactions. 相似文献
5.
Roland Schmidt Erik McNellis Wolfgang Freyer Daniel Brete Tanja Gießel Cornelius Gahl Karsten Reuter Martin Weinelt 《Applied Physics A: Materials Science & Processing》2008,93(2):267-275
Self-assembled monolayers (SAMs) of 4-trifluoromethyl-azobenzene-4′-methyleneoxy-alkanethiols (CF3– C6H4–N=N–C6H4–O–(CH2)
n
–SH on (111)-oriented poly-crystalline gold films on mica were examined by X-ray photoelectron spectroscopy (XPS) and X-ray
absorption spectroscopy (XAS). The spectra are analyzed with the help of density-functional-theory calculations of the isolated
molecule. Only one doublet is detected in the sulphur 2p spectra of the investigated SAMs, consistent with a thiolate bond of the molecule to the gold surface. The C 1s XP spectra and the corresponding XAS π
* resonance exhibit a rich structure which is assigned to the carbon atoms in the different chemical surroundings. Comparing
XPS binding energies of the azobenzene moiety and calculated initial-state shifts reveals comparable screening of all C 1s core holes. While the carbon 1s XPS binding energy lies below the π
*-resonance excitation-energy, the reversed order is found comparing core ionization and neutral core excitation of the nitrogen 1s core-hole of the azo group. This surprising difference in core-hole binding energies is interpreted as site-dependent polarization
screening and charge transfer among the densely packed aromatic moieties. We propose that a quenching of the optical excitation
within the molecular layer is thus one major reason for the low trans to cis photo-isomerization rate of azobenzene in aromatic-aliphatic
SAMs. 相似文献
6.
7.
The phenomenological amplitude for the reaction πN→ππN fixed by fittings to the experimental data in the energy region 0.300 ≤P
Lab≤ 500 MeV/c is used for modelling the Chew–Low extrapolation and Olsson–Turner threshold approach. It is shown that the uncritical
application of the former results in enermous theoretical errors, the extracted values being in fact random numbers. The results
of the Olsson–Turner method are characterized by significant systematic errors coming from unknown details of the isobar physics.
Received: 10 December 1997 相似文献
8.
Considering two assumptions on the molecular state, i.e. the S-wave Λ̄–K- and S-wave Σ̄0–K- molecular states, we study the possible decays of N̄X(1625) that include N̄X(1625)→K-Λ̄,π0p̄,ηp̄,π-n̄. Our results indicate that (1) if N̄X(1625) is the Λ̄–K- molecular state, K-Λ̄ is the main decay mode of N̄X(1625), and the branching ratios of the rest decay modes are tiny; (2) if N̄X(1625) is the Σ̄0–K- molecular state, the branching ratio of N̄X(1625)→K-Λ̄ is one or two orders smaller than that of N̄X(1625)→π0p̄,ηp̄,π-n̄. Thus the search for N̄X(1625)→π0p̄,ηp̄,π-n̄ will be helpful to shed light on the nature of N̄X(1625).
PACS 13.30.Eg, 13.75.Jz 相似文献
9.
Chemiluminescence (CL) of the reaction system tetracycline–H2O2–Fe(II)/(III)–Eu(III) was used for the determination of tetracycline hydrochloride in water, pharmaceutical preparations,
and honey. The CL spectrum registered for this system shows emission bands typical of Eu(III) ions, with a maximum at λ ∼ 600 nm,
corresponding to the electronic transitions of 5D0 → 7F1 and 5D0 → 7F2. A strong chemiluminescence intensity characteristic of europium(III) ions in the system tetracycline–H2O2–Fe(II)/(III)–Eu(III), as contrasted to the emission of the system tetracycline–H2O2–Fe(II)/(III) without Eu(III), proves that the Eu(III) ion plays the role of a chemiluminescence sensitizer, accompanying
tetracycline oxidation in the Fenton system (H2O2–Fe(II)/(III)). A linear dependence was observed for the integrated CL light intensity on the tetracycline concentration in
the range of 2 × 10−7 to 3 × 10−5 mol l−1 with the detection limit of 5 × 10−8 mol l−1 in aqueous solution. 相似文献
10.
Xiaoyi Li Yiqun Wu Donghong Gu Fuxi Gan 《Applied Physics A: Materials Science & Processing》2011,102(3):719-724
Three novel metal(II) complexes, CoL2, NiL2 and CuL2 (L = (Z)-4-(2-(1,3-dimethyl-5-oxo-1H-pyrazol-4(5H)-ylidene)hydrazinyl)-1,5-dimethyl-2-phenyl-1,2-dihydropyrazol-3-one were
synthesized. Their structures were postulated based on elemental analyses, 1H NMR, ESI-MS, FT-IR spectra and UV-vis spectra. The effect of different central metal(II) ions on absorption bands of the
metal(II) complexes in CHCl3 solutions was researched. The result indicates that the bathochromic shift is CuL2 > NiL2 > CoL2. The absorption properties of thin films and thermal stability of these complexes are also discussed. In addition, the optical
constants (complex refractive index N=n+ik) and thickness of the complex thin films on polished single-crystal silicon substrates were measured by spectroscopic ellipsometry.
Results indicate that the metal(II) complexes would be a promising recording medium candidate for blu-ray recordable optical
storage system due to good absorption at 405 nm, high thermal stability and sharp thermal decomposition, and a high n values of 1.35–1.45 and a low k values of 0.33–0.39. 相似文献
11.
12.
Chemiluminescence of the system containing Tb(III) ions, histidine and bromate ions in acid solution was studied. The kinetic
curves and CL emission spectra of the system were discussed. The emission spectrum of the histidine–Tb(III)–KBrO3–H2SO4 system revealed two emission maxima at ∼490 and 550 nm, characteristic of Tb(III) ions. Values of lifetimes of the Eu(III)
excited states in Eu(III)–histidine system have shown that the histidine formed ML and ML2 complexes in neutral solution and did not make them in acidic environment. On the basis of the results, a possible mechanism
of reaction system: histidine–Tb(III)–KBrO3–H2SO4 is presented. 相似文献
13.
D.V. Bugg 《The European Physical Journal C - Particles and Fields》2007,52(1):55-74
Claims have been made that f0(1370) does not exist. The five primary sets of data requiring its existence are refitted with suitable Breit–Wigner amplitudes.
Major dispersive effects due to the opening of the 4π threshold are included for the first time; the σ→4π amplitude plays
a strong role. Crystal Barrel data on p̄p→3π0 at rest require f0(1370) signals of at least 32 and 33 standard deviations (σ) in 1S0 and 3P1 annihilation respectively. Furthermore, they agree within 5 MeV for mass and width. Data on p̄p→ηηπ0 agree and require at least a 19σ contribution. This alone is sufficient to demonstrate the existence of f0(1370). BES II data for J/Ψ→φπ+π- contain a visible f0(1370) signal >8σ. In all cases, a resonant phase variation is required. Cern–Munich data for ππ elastic scattering are fitted
well with the inclusion of some mixing between σ, f0(1370) and f0(1500). Values of Γ2π for f2(1565), ρ3(1690), ρ3(1990) and f4(2040) are determined.
PACS 13.25.Gv; 14.40.Gx; 13.40.Hq 相似文献
14.
V. Bernard N. Kaiser Ulf-G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》1999,4(3):259-275
We evaluate the threshold matrix–element for the reaction pp→ppπ0 in a fully relativistic Feynman diagrammatic approach. We employ a simple effective range approximation to take care of the
S–wave pp final–state interaction. The experimental value for the threshold amplitude A = (2.7 −i0.3) fm4 can be reproduced by contributions from tree level chiral (long–range) pion exchange and short–range effects related to vector
meson exchanges, with ω-exchange giving the largest individual contribution. Pion loop effects appear to be small. We stress
that the commonly used heavy baryon formalism is not applicable in the NN–system above the pion production threshold due to
the large external momentum, |p|≃ (Mm
π)−1/2, with M and m
π the nucleon and the pion mass, respectively. We furthermore investigate the reaction pp→pnπ+ near threshold within the same approach. We extract from the data the triplet threshold amplitude as B = (2.8 −i1.5) fm4. Its real part can be well understood from (relativistic) tree level meson–exchange diagrams. In addition, we investigate
the process pp→ppη near threshold. We use a simple factorization ansatz for the ppη final–state interaction and extract from the data the modulus of the threshold amplitude, |C|= 1.32 fm4. With g
ηN= 5.3, this value can be reproduced by (relativistic) tree level meson–exchange diagrams and η–rescattering, whose strength
is fixed by the ηN scattering length. We also comment on the recent near threshold data for η′–production.
Received: 27 November 1998 相似文献
15.
G.I. Lykasov W. Cassing A. Sibirtsev M.V. Rzjanin 《The European Physical Journal A - Hadrons and Nuclei》1999,6(1):71-81
We calculate the elastic and inelastic ωN→ωN, →πN, →ρN, →ρπN, →ππN, →σN reactions within a boson exchange approximation where the ωρπ coupling constant and form factor are fixed by the reaction
πN→ωN in comparison to the experimental data. We find rather large ωN cross sections at low relative momenta of the ω-meson which
leads to a substantial broadening of the ω-meson width in nuclear matter. The implications of the ωN final state interactions are studied for ω production in 12C +12C, 40Ca +40Ca and 58Ni +58Ni reactions at about 2 · A GeV within the HSD transport approach; the drastic changes of the transverse mass spectra relative
to a general m
T-scaling (for π0 and η mesons) might be controlled experimentally by the TAPS Collaboration.
Received: 28 April 1999 / Revised version: 7 June 1999 相似文献
16.
F.O. Talbot J.P. Simons 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(3):389-398
Mass-resolved resonant two photon ionisation (R2PI) and infrared ion dip spectra have been recorded for 4-phenylimidazole
(4PI) and its singly and multiply hydrated clusters 4PI(H2O)n = 0 - 4, under supersonic expansion conditions. In the case of 4PI(H2O)0,1, it has also been possible to record infrared spectra in both the ground (S0) and excited (S1) states. Combining the experimental data with the results of ab initio calculations has led to the structural assignment of each cluster. In each case, the water molecules bind primarily to the
NH site of the imidazole ring. Clusters with n≥ 2 incorporate linear water chains, in which the proton donating terminus bridges either to the π-electron system (n = 2) or to the >N: atom site (n = 3, 4) on the imidazole ring. Despite the creation of a “water wire”, connecting the donor and acceptor sites of imidazole,
there is no evidence of proton transfer in either the ground or excited state.
Received 20 December 2001 Published online 13 September 2002 相似文献
17.
Guoqing Zhang Shin Han Kim Ruffin E. Evans Byeong Hyo Kim J. N. Demas Cassandra L. Fraser 《Journal of fluorescence》2009,19(5):881-889
A class of aryl trifluoromethyl-containing β-diketones were synthesized via one step Claisen condensation. These π-conjugated
diketones exhibit strong solvatochromism from intramolecular donor-acceptor charge transfer (CT). In addition, fluorescence
quantum yields (ϕf) and lifetimes (τf) were measured in different solvents. Diketones exhibit bathochromic shifts in emission spectra with increasing solvent polarity.
Fluorescence changes upon Group II metal binding were also studied. Despite the relatively simple structure, the anthracene-CF3 diketone, atm, has strong binding affinity for Mg2+. A 70 nm blue shift and sixfold increase in intensity were observed upon addition of only one equivalent MgCl2 in ethanol solution. It also shows selectivity for Mg2+ binding even in the presence of excess Ca2+. Association constant (Ka) calculations suggest atm has two orders of magnitude stronger chelation for divalent magnesium than for calcium. These findings
make atm an attractive starting point for molecular probe and light emitting material design. 相似文献
18.
We present the results of simultaneous analysis of the S-wave ππ spectra in the reactions π
−
p → (ππ)S
n at p
lab=38 GeV/c (GAMS) and π
−
p → (ππ)S
n at p
lab=18 GeV/c (E852 Collaboration) at moderate momenta transferred to the nucleon, |t| ≲ 1.5 (GeV/c)2. The t distributions are described by the Reggeized π and a
1 exchanges provided by the leading and daughter trajectories, while the M
ππ
spectra are determined by a set of scalar-isoscalar resonances. With M
ππ
distributions averaged over different t intervals, we have found several solutions given by different t-channel-exchange mechanisms at |t| ∼ (0.5–1.5) (GeV/c)2, with resonance parameters close to each other. We conclude that, despite a poor knowledge of the structure of the t exchange, the characteristics of resonances such as masses and widths can be reliably determined using the processes under
discussion. As to pole positions, we have found (1031±10)−i(35±6) MeV for f
0(980) and (1315±20)−i(150±30) MeV for f
0(1300).
From Yadernaya Fizika, Vol. 66, No. 5, 2003, pp. 960–972.
Original English Text Copyright ? 2003 by Anisovich, Sarantsev.
This article was submitted by the authors in English. 相似文献
19.
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
20.
K. Koizumi M. Shoji Y. Kitagawa H. Ohoyama T. Kasai K. Yamaguchi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(1):193-197
The electronic structure and effective exchange integrals (J ab)
between two manganese (III) ions of porphyrin dimer (PPMn(III)–OH–Mn(III)PP)
were examined by using unrestricted hybrid DFT (UHDFT) methods. The
dependence of Jab on bond angle between two manganese (
Mn–OH–Mn) is
also calculated to elucidate orbital overlap effect for Jab value in the system. Natural orbital analysis is performed to explain the overlap effect in terms of the instability of the
π, σ and δ orbitals by using diradical character. 相似文献