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1.
Fluorescence and excitation spectra of all-trans-2,4,6,8-decatetraene vapour have been measured at different buffer gas pressures from 0 to 1.07 × 10 5 Pa (800 Torr). The quantum yield of the S 1 fluorescence (Φ F(S 1)) increases with increasing the buffer gas pressure, while that of the S 2 fluorescence (Φ F(S 2)) decreases slightly. Φ F(S 1) decreases significantly with increasing the excitation energy under the collision free condition, while Φ F(S 2) decreases only slightly. The pressure dependence of the fluorescence yields is interpreted in terms of the relaxation model involving the reversible internal conversion between S 1 and S 2 and the vibrational relaxation in the S 1 manifold. The reverse S 1 → S 2 internal conversion rate is shown to be very slow compared with the forward S 2 → S 1 internal conversion rate. 相似文献
2.
Laser induced fluorescence spectra are reported for samples of natural selenium and of the separated 78Se and 80Se isotopes in Ar and Kr matrices. The B(0 u+) → X(0 g+) and B(1 u) → X(1 g) systems of Se 2, already known in the gas, are observed by both single photon and biphotonic excitation considerably red-shifted in the matrices. The A(0 u+) → X(0 g+) emission of Se 2, not observed in the vapor, appears in the matrices with its origin near 15 100 cm ?1. Another system with ν00 = 24 429 cm ?1 and ω″ e = 538 cm ?1 is thought to belong most probably to some polyatomic Se n molecule. 相似文献
3.
For the first time, direct experimental evidence of a new mechanism for the quenching of fluorescence of organic ligands (L) in complex compounds with lanthanide ions (Ln3+) is obtained. By analogy with the mechanism of luminescence quenching upon pair interactions of Ln3+ ions in inorganic systems, this mechanism is called the cross-relaxation mechanism. The experiments are performed with complexes of Tb3+ with dianions of halogen-substituted fluoresceins (HSFs): 4,5-dibromo-and 4,5-diiodofluorescein, eosin B, eosin, erythrosin, and Rose Bengal in dimethyl sulfoxide. In accordance with this mechanism—exchange energy transfer, L2?(*S
1), Tb3+(7
F
6)→L2?(T
1), Tb3+(7
F
5, 4), allowed by the spin selection rules—an increase in the quantum yield of formation of the triplet state (ΦT) of a ligand L2? and a decrease in the quantum yield of fluorescence (Φfl) are found to take place upon complexation. The efficiency of this process amounts to ~1 in accordance with the equality Φfl+ΦT=1, valid for solutions of HSFs. The possibility of other processes leading to a similar effect, specifically, recharging of the system (as for complexes of HSFs with Eu3+ and 3+) is considered. An example of inductive resonance interactions in complexes of HSFs with Pr3+ is given. The manifestation of equilibrium between outer-sphere and inner-sphere complexes in the photophysics of complexes of metals with HSFs is discussed. 相似文献
4.
推导了S 2分子B″ 3Π u态的合理离解极限.用Gaussian 94 QCISD(T)方法和6-311++G **基组计算了S 2分子B″ 3Π u以及X 3Σ -g态的势能曲线.给出了S 2分子B″ 3Π u态的Murrell-Sorbie势能函数和光谱常数.B″ 3Π u与B 3Σ -u态在排斥支重叠范围大;同时,B″ 3Π u与X 3Σ -g态有相同离解极限,因而,在吸引支有重叠.讨论了B″ 3Π u与B 3Σ -u和X 3Σ -g态相互作用的特征.
关键词: 相似文献
5.
在室温下,测量了Er:Tm:NaY(WO 4) 2晶体的吸收光谱、激发光谱、发射光谱以及上转换发光,并运用J-O理论对测量的结果进行了计算,得出了Er:Tm:NaY(WO 4) 2晶体的强度参数.报道了Tm,Er离子间特殊的能量传递和相关上转换,解释了离子间的能级跃迁过程.同时,对于Er增强Tm离子近红外发光的特性也作了充分研究.
关键词:
4) 2晶体')" href="#">Er:Tm:NaY(WO 4) 2晶体
吸收光谱
发射光谱
激发光谱
上转换 相似文献
6.
The photophysics and photochemistry of pyrazine (C 4H 4N 2, D 2h) after excitation to the S2 (1 1B 2u, 1ππ*) electronic state were studied by using the resonance Raman spectroscopy and complete active space self‐consistent field method calculations. The B‐band resonance Raman spectra in cyclohexane solvent were obtained at 266.0, 252.7, and 245.9 nm excitation wavelengths to probe the structural dynamics of pyrazine in the S2 (1 1B 2u, 1ππ*) state. Three electronic states 1 1B 3u, 1 1B 1g, and 1 1B 2g were found to couple with the S2 (1 1B 2u, 1ππ*) state. Two conical intersection (CI) points CI[ S2(B 2u)/ S1(B 3u)] and CI[ S1/ S0] and one transition state of the isomerization between pyrazine and pyrimidine were predicted to play important roles in the photochemistry of pyrazine. On the basis of the calculations, the mechanism of the photoisomerization reaction between pyrazine and pyrimidine has been proposed. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
7.
A rotationally resolved ultrahigh-resolution fluorescence excitation spectrum of the S 1 ← S 0 transition of perylene has been observed using a collimated supersonic jet technique in conjunction with a single-mode UV laser. We assigned 1568 rotational lines of the band, and accurately determined the rotational constants. The obtained value of inertial defect was positive, accordingly, the perylene molecule is considered to be planar with D2h symmetry. We determined the geometrical structure in the S 0 state by ab initio theoretical calculation at the RHF/6-311+G(d,p) level, which yielded rotational constant values approximately identical to those obtained experimentally. Zeeman broadening of each rotational line with the external magnetic field was negligibly small, and the mixing with the triplet state was shown to be very small. This evidence indicates that intersystem crossing (ISC) in the S 11B2u state is very slow. The rate of internal conversion (IC) is also inferred to be small because the fluorescence quantum yield is high. The rotational constants of the S 11B2u state were very similar to those of the S 01Ag state. The slow internal conversion (IC) at the S 1 zero-vibrational level is attributed to a small structural change upon electronic transition. 相似文献
8.
Using Czochralski (CZ) pulling method, an Er 3+/Yb 3+-codoped NaY(WO 4) 2 crystal was prepared. Absorption spectra, emission spectra and excitation spectra of this crystal were measured at room temperature. Some optical parameters, such as intensity parameters, spontaneous emission probabilities and lifetimes, were calculated from absorption spectra with Judd-Ofelt (J-O) theory. Upconversion luminescence excited by a 970 nm diode laser was studied. In this crystal, green upconversion luminescence is particularly intensive. Energy transfer mechanisms that play an important role in upconversion processes were analyzed. Two cross-relaxation processes: 4G 11/2 + 4I 9/2 → 2H 11/2 (or 4S 3/2) + 2H 11/2 (or 4S 3/2), and 4G 11/2 + 4I 15/2 → 2H 11/2 (or 4S 3/2) + 2I 13/2, which contribute to the intensive green luminescence under 378 nm excitation, were put forward. Background energy transfer 4G 11/2(Er 3+) + 2F 7/2(Yb 3+) → 4F 9/2(Er 3+) + 2F 5/2(Yb 3+) was also demonstrated. 相似文献
9.
Novel Eu 3+, Ce 3+ activated NaBa 4(BO 3) 3 phosphors were synthesized by solid-state reactions. The excitation spectrum of NaBa 4(BO 3) 3:Ce 3+ consists of an intense band peaking at 350 nm and a weak band in the higher energy side, and the emission spectrum exhibits a blue band with a maximum at about 420 nm. The Eu 3+ emission in NaBa 4(BO 3) 3 consists of the transitions from 5D0 to 7FJ, and the excitation spectrum consists of broad excitation band peaking at 270 nm and some intense narrow lines. The optimum doped concentration, the critical distance of the concentration quenching, and the fluorescence lifetime have also been investigated. 相似文献
10.
A single-mode autoscan laser spectrometer operating in the ultraviolet in combination with a collimated molecular beam was used to measure high resolution fluorescence excitation spectra of the CS 2 V 1B 2 ← X 1Σ + g transition under collision-free conditions, and the effects of a magnetic field were measured. Rotational and vibrational levels were fully resolved, and Zeeman splittings were observed in many of the perturbed lines. The Zeeman interaction was observed to induce new perturbation, which induces new transitions, level splitting, and energy shift. When the magnetic field strength was changed, the magnitude of the interaction, which was observed in the absence of a magnetic field, changed dramatically depending on the energy shifts of the Zeeman components. It is shown that the V 1B 2( 1Δ u) state is mixed with the B 2( 3A 2) component by first-order spin-orbit interaction, and through the mixed component, the Zeeman interaction between the V 1B 2( 1Δ u) and 3A 2( 3Δ u) states is induced. Large Zeeman splittings were observed for most of the background lines of weak intensity, and this demonstrates that the background levels are levels of the 3A 2( 3Δ u) state. The fluorescence decays of single Zeeman components were observed to be single exponential. The lifetimes of the perturbing 3A 2( 3Δ u) levels were determined by deperturbation analysis. Triplet-triplet 3A 2( 3Δ u) → 3B 2( 3Σ + u) emission was confirmed. It was demonstrated that the quenching of the V 1B 2 → X 1Σ + g fluorescence by a magnetic field was caused by mixing of the 3A 2 state with the V 1B 2 state and the resulting increase of triplet-triplet emission. In a time-dependent picture, the intersystem crossing from the 1B 2( 1Δ u) and 3A 2( 3Δ u) states is enhanced by the magnetic field. 相似文献
11.
In this paper, the equilibrium geometry, harmonic frequency and dissociation energy of S2^- and S3^- have been calculated at QCISD/6-311++G(3d2f) and B3P86/6-311++G(3d2f) level. The S2^- ground state is of 2IIg, the S3^- ground state is of 2B1 and S3^- has a bent (C2v) structure with an angle of 115.65° The results are in good agreement with these reported in other literature. For S3^- ion, the vibration frequencies and the force constants have also been calculated. Base on the general principles of microscopic reversibility, the dissociation limits has been deduced. The Murrell-Sorbie potential energy function for S2^- has been derived according to the ab initio data through the least- squares fitting. The force constants and spectroscopic data for S2^- have been calculated, then compared with other theoretical data. The analytical potential energy function of S3^- have been obtained based on the many-body expansion theory. The structure and energy can correctly reappear on the potential surface. 相似文献
12.
In polar and nonpolar solvents, tetrahydroisoquinoline emits S 2 (ππ 1) → S 0 and S 1 (ππ 1) → S 0 dual fluorescence and T 1 (ππ 1) → S 0 phosphorescence on S 2 (ππ 1) ← S 0 excitation. When excited by S 1 (ππ 1) ← S 0 the molecule yields S 1 (ππ 1) → S 0 fluorescence and T 1 (ππ 1) → S 0 phosphorescence in nonpolar solvent but only fluorescence in polar solvents. Probable participation of intermediate S 1 (nπ 1), T 1(nπ 1) states in intersystem crossing and internal conversion processes and its significance in interpreting the results are discussed. 相似文献
13.
Anomalous S 2 → S 0 fluorescence and T 2 → S 0 phosphorescence have been found in several triphenylmethane derivatives. This phenomenon can be explained by a large energy gap between the S 2 and S 1 levels, approximately 14000 cm ?1. Some of the investigated compounds exhibit also a normal long-wave fluorescence in spite of the fact, that the S 2 ? S 1 energy gap does not change significantly. However, in these cases absorption spectra reveal a high oscillator strength of the S 1 → S 0 transition. The coordination of a lanthanide ion quenches in several cases the normal S 1 → S 0 fluorescence whereas the S 2 → S 0 one is not affected significantly. 相似文献
14.
The excitation of odd levels of the thulium atom, spontaneous transitions from which terminate at the 4 f
13( 2
F
o)6 s6 p( 3
P
o) (7/2, J
2) levels with J
2 = 0, 1, is studied by the method of extended crossing beams. Fifty four excitation cross sections are measured at an excitation
electron energy of 50 eV. Seven optical excitation functions are recorded in the electron energy range of 0–200 eV. 相似文献
15.
In this work the deexcitation of the B3Π +( Ou+), v′ = 14 level of I 2 after pulsed laser excitation has been studied. The quenching cross sections by collisions with I 2, H 2, CO, and CH 4 have been measured. The experimental results are 190 ± 14, 2.5 ± 0.3, 15.1 ± 0.4, and 18.0 ± 0.6 Å 2, respectively. These values are compatible (within 30%) with the semiempirical scaling law of proportionality with the product of polarizability and the square root of reduced mass. 相似文献
16.
The photoluminescence and excitation spectra of Pr 3+ activated LiLaP 4O 12 has been investigated in the 10-300 K temperature region. At all temperatures, the luminescence consists of optical transitions emanating from both the Pr 3+ 4f 15d 1 and the 1S 0 states. However, at low temperatures the emission spectrum is dominated by the intraconfiguration emission transitions emanating from the Pr 3+1S 0 state. With increasing temperature, there is an exchange of intensity between the two emitting states; emission transitions from the 1S 0 state exhibit strong intensity quenching while the 4f 15d 1→4f 2 emission transitions reveal intensity gain. These results are explained on the basis of thermal population of the 4f 15d 1 state by the 1S 0 state. The energy barrier of 0.05 eV (403 cm −1) for the nonradiative process is determined from the temperature dependence of the 1S 0 lifetime. 相似文献
17.
This work computed the potential energy curves of 19 Λ-S states, which arose from the first five dissociation limits of BC + cation, B +( 1S g) + C( 3P g), B +( 1S g) + C( 1D g), B +( 1S g) + C( 1S g), C +( 2P u) + B( 2P u), and B +( 1S g) + C( 5S u). The calculations were done for internuclear separations from 0.08 to 1.07 nm. The potential energy curves of 36 Ω states yielded from these Λ-S states were also calculated. Core-valence correlation and scalar relativistic correction, basis set extrapolation as well as Davidson correction were accounted for. Of these Λ-S states, the c 1Σ +, D 3Π, 2 1Π, 2 3Σ +, 2 1Δ, 3 1Σ +, and 4 1Σ + had double wells; the 3 3Π and 3 1Π states had three wells; the C 3Σ ? and D 3Π states were inverted with the spin-orbit coupling effect included; and the second wells of c 1Σ +, D 3Π and 3 1Σ + states, the second and the third wells of 3 3Π state as well as the third well of 3 1Π state were very weakly bound, which well depths were smaller than 400 cm ?1. The spectroscopic parameters were determined for all the states. The vibrational properties were predicted only for some weakly bound states. The spin-orbit coupling effect on the spectroscopic parameters was evaluated. 相似文献
18.
以Nd:YAG激光器的二倍频输出光为抽运光,其三倍频输出抽运的光学参量发生/放大器输出光为探测光,利用光学-光学双色双共振多光子离化光谱技术(OODR-MPI),获得了NO 2分子在605—675nm探测光波长范围内的多光子离化激发谱. 通过对NO 2分子离化机理的分析,确定了在此波长区间,NO 2分子经1+3+1双共振多光子过程离化,离化通道为NO 2(X 2A 1) hν
关键词:
2')" href="#">NO 2
光学-光学双共振多光子离化谱
里德伯态
分子常数 相似文献
19.
The dissociation of NH 3 into electronic ground-state fragments NH 2( 2B 1) + H by high-intensity CO 2 laser radiation has been observed under essentially collision free conditions and as a function of NH 3 pressure, using laser fluorescence excitation for the NH 2 detection. Luminescence from excited NH 2 ( 2A 1) produced directly by the CO 2 laser has also been observed. The relative yield of NH 2 ( 2A 1) is estimated to be smaller than that of NH 2 ( 2B 1) by several orders of magnitude. 相似文献
20.
A NIR excitation of Er 3+ doped Lithium modified tellurite (Li:TeO 2) glass results in antistokes fluorescent emission near 380, 530, 551 and 654 nm (ultraviolet, green and red regions) in addition to NIR Stokes emission. The antistokes emissions are ascribed to transition from the excited 4G 11/2, 4S 3/2( 2H 11/2) and 4F 9/2 levels in Er 3+. The excitation involves three and two incident photons. On excitation with the green laser line at 532 nm also leads to similar emissions. The mechanisms involved in these processes are discussed on the basis of the known energy level diagram and the upconversion efficiency has been calculated. Lifetime of the 4S 3/2 level has been measured. The temperature dependence of the upconversion process has also been investigated. 相似文献
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