共查询到20条相似文献,搜索用时 25 毫秒
1.
Leonid Dolgov Valter Kiisk Valter Reedo Siim Pikker Ilmo Sildos Jaak Kikas 《Central European Journal of Physics》2011,9(2):542-546
Composite material based on a TiO2 matrix doped with Sm3+ ions and co-doped with silver was investigated. Samarium ions together with nano- and micro-aggregates of silver were incorporated
into the titanium alkoxide during the sol-gel process. Samarium ions were excited either directly (λ
exc = 488 nm) or through the TiO2 host (λ
exc = 355 nm). It was revealed that samarium fluorescence (λ
exc = 488 nm) in gelled TiO2 films is enhanced by up to 20 times in the vicinity of silver inclusions. Sensitizing and plasmonic mechanisms of enhancement
in Sm3+ fluorescence are discussed. 相似文献
2.
Ye. V. Baklanov V. P. Chebotayev 《Applied Physics A: Materials Science & Processing》1977,13(1):97-99
First cw laser oscillation with thresholds below 1 mW was observed for various B1Пu → X1
∑
g
+
transitions of diatomic molecular sodium excited by different argon laser lines in the range of 454–488 nm. For pump powers
of 0.5 W output powers up to 3 mW and single-pass gain up to 0.1 cm−1 were obtained. Some properties of the heat pipe laser system are discussed. 相似文献
3.
C. L. Sun J. F. Li C. H. Hu H. M. Jiang Z. K. Jiang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(2):303-306
Ultraviolet upconversion fluorescence band (260–350 nm) has been observed
from Pr3+:Y2SiO5 pumped by Ar+ ion laser (488 nm). Power
dependence of the fluorescence emitted from 4f5d, 3P0 and
1D2 were measured. The upconversion mechanism was analyzed using
the rate equations with a simplified three level model. It appears that
excited state absorption (ESA) is the dominant upconversion process for
lower Pr3+ concentration and energy transfer upconversion (ETU) is
dominant for higher Pr3+ concentration. 相似文献
4.
The fluorescence spectra of CS2 and SO2 have been studied at three incident photon wavelengths of 121.6, 73.6–74.4 and 58.4 nm and relative production cross sections
for different product states have been measured. The CS(A
1Π→X
1Σ+) system between 240 and 290nm has been obtained when CS2 is photoexcited at 121.6nm whereas CS
2
+
(B
2Σ
u
+
→X
2Π
g
) and CS
2
+
(A
2Π
u
→X
2Π
g
) systems have been produced between 276 and 295 and 437 and 555nm respectively when excited by both the incident photon wavelengths
of 73.6–74.4 and 58.4nm. The fluorescence spectra of SO2 obtained at 121.6 and 73.6–74.4nm include the vibrational bands of SO(A
3Π→X
3Σ−) and SO(B
2Π−→X
3Σ−) systems from 240 to 268 and 268 to 442nm respectively whereas the emission spectrum at 58.4nm, has contributions from the
two SO systems and SO+(A
2Π→X
2Π) system. In all these emission spectra, the fluorescence bands of different systems have been analyzed and their relative
production cross sections have been measured. The results obtained in the present investigations have been compared with a
few recent reliable measurements reported in literature. 相似文献
5.
Jesús?álvarez-Ruiz Marien?López-Arias Rebeca?de?Nalda Margarita?Martín Andrés?Arregui Luis?Ba?ares 《Applied Physics A: Materials Science & Processing》2009,95(3):681-687
The formation of cationic clusters in the laser ablation of CdS targets has been investigated as a function of wavelength
and fluence by mass spectrometric analysis of the plume. Ablation was carried out at the laser wavelengths of 1064, 532, 355,
and 266 nm in order to scan the interaction regimes below and above the energy band gap of the material. In all cases, the
mass spectra showed stoichiometric Cd
n
S
n
+ and nonstoichiometric Cd
n
S
n−1+, Cd
n
S
n+1+, and Cd
n
S
n+2+ clusters up to 4900 amu. Cluster size distributions were well represented by a log-normal function, although larger relative
abundance for clusters with n=13, 16, 19, 34 was observed (magic numbers). The laser threshold fluence for cluster observation was strongly dependent on
wavelength, ranging from around 16 mJ/cm2 at 266 nm to more than 300 mJ/cm2 at 532 and 1064 nm. According to the behavior of the detected species as a function of fluence, two distinct families were
identified: the “light” family containing S2+ and Cd+ and the “heavy” clusterized family grouping Cd2+ and Cd
n
S
m
+. In terms of fluence, it has been determined that the best ratio for clusterization is achieved close to the threshold of
appearance of clusters at all wavelengths. At 1064, 532, and 355 nm, the production of “heavy” cations as a function of fluence
showed a maximum, indicating the participation of competitive effects, whereas saturation is observed at 266 nm. In terms
of relative production, the contribution of the “heavy” family to the total cation signal was significantly lower for 266 nm
than for the longer wavelengths. Irradiation at 355 nm in the fluence region of 200 mJ/cm2 has been identified as the optimum for the generation of large clusters in CdS. 相似文献
6.
Two simple, sensitive and specific fluorimetric methods have been developed for the determination of some sulphur containing
compounds namely, Acetylcysteine (Ac), Carbocisteine (Cc) and Thioctic acid (Th) using terbium Tb+3 and uranium U+3 ions as fluorescent probes. The proposed methods involve the formation of a ternary complex with Tb+3 in presence of Tris-buffer method (I) and a binary complex with aqueous uranyl acetate solution method (II). The fluorescence
quenching of Tb+3 at 510, 488 and 540 nm (λex 250, 241 and 268 nm) and of uranyl acetate at 512 nm (λex 240 nm) due to the complex formation was quantitatively measured for Ac, Cc and Th, respectively. The reaction conditions
and the fluorescence spectral properties of the complexes have been investigated. Under the described conditions, the proposed
methods were applicable over the concentration range (0.2–2.5 μg ml−1), (1–4 μg ml−1) and (0.5–3.5 μg ml−1) with mean percentage recoveries 99.74±0.36, 99.70±0.52 and 99.43±0.23 for method (I) and (0.5–6 μg ml−1), (0.5–5 μg ml−1), and (1–6 μg ml−1) with mean percentage recoveries 99.38±0.20, 99.82±0.28 and 99.93±0.32 for method (II), for the three cited drugs, respectively.
The proposed methods were successfully applied for the determination of the studied compounds in bulk powders and in pharmaceutical
formulations, as well as in presence of their related substances. The results obtained were found to be in agree statistically
with those obtained by official and reported ones. The two methods were validated according to USP guidelines and also assessed
by applying the standard addition technique. 相似文献
7.
A. Brockhinke A.T. Hartlieb K. Kohse-Höinghaus D.R. Crosley 《Applied physics. B, Lasers and optics》1998,67(5):659-665
2 in a flame, excited by a tunable KrF laser near 248 nm. The first comprises several P and R lines of the (1,0) band of the
e 3Πg-a 3Πu Fox–Herzberg system, with fluorescence bands extending past 350 nm. The second is the band head region of the (7,1) band
of the D 1Σu
+←B′ 1Σg
+ system, with fluorescence at 232 nm from D to the X 1Σg
+ ground state. Neither band has been previously observed in any environment. The flame in these experiments is highly sooting,
and the C2 seen here is likely produced by laser vaporization of the soot with subsequent laser photolysis of a C2 precursor. In a rich flame, this fluorescence could cause interferences in other studies such as KrF laser Raman scattering.
Moreover, signal level calculations suggest native C2 near 10 ppm could be readily observed using the Fox–Herzberg excitation. Raman measurements of major species (X≥0.01) in
the same flame, using the KrF laser, are in good agreement with a model prediction.
Received: 2 April 1998/Revised version: 8 June 1998 相似文献
8.
This paper deals with the photo-induced fluorimetric determination of the herbicide Fluometuron with the aid of a continuous-flow
assembly of the emergent and new methodology known as Multicommutation which was provided with an on-line photoreactor. Maximum
fluorescence intensity was observed at basic pH solutions, 1×10−4 mol l−1 NaOH, after 1.4 min of irradiation and being the maximum at λexc 247.0 nm and λem 325.0 nm.
The influence of different experimental parameters either chemical (pH, surfactants presence, solvent polarity and temperature)
or hydrodynamic (time of photo-degradation, size and number of different segments and flow-rate) was tested.
The linear dynamic range was from 0.01 to 4.0 mg l−1 of Fluometuron; the inter-day reproducibility (as R.S.D.) of the slope was 0.001% and 1.7% from the peaks intra-day reproducibility.
A large series of potential interferents was studied and finally the method was applied to human urine, soil, formulation
and water samples. 相似文献
9.
A selective fluorescent cesium optode on a chromoionophore consisting of anthracene covalently linked through an imine bond
to a 15-crown-5 derivative has been reported. In the present system, 15-crown-5 derivative including anthracene was used a
fluoroionophore. The fluorescence response mechanism is based on the photo-induced electron transfer (PET) from the lone pair
of electrons of the nitrogen to the anthracene group and inhibition of PET system by cesium binding while increasing the fluorescence
intensity. Emission intensity 15-crown-5 anthracene was measured at 500 nm with absorbance at 400 nm in CH3CN–H2O (1:1) media. The method shows a very good selectivity and sensitivity for cesium with respect to other cations such as K+, Na+ and Li+ with linear range and detection limit of 5.0 × 10−5 to 5.0 × 10−1M and 3.0 × 10−6M respectively. 相似文献
10.
A. Majkić G. Poberaj R. Degl’Innocenti M. Döbeli P. Günter 《Applied physics. B, Lasers and optics》2007,88(2):205-209
We report on the production and fluorescence of active channel waveguides in Cr:LiSrAlF6. We have produced ∼10 μm wide and 5 μm high channel waveguides by He+ ion implantation, lithographic patterning and subsequent Ar+ ion sputtering. Diode-pumped waveguides emitted 13 μW of fluorescence light with a spectrum ranging from 760 nm to 900 nm
at a pump power of 165 mW and a pump wavelength of 660 nm. The compact and cheap optical pump source is a main advantage of
this fluorescence material. This makes Cr:LiSrAlF6 channel waveguides a suitable candidate for a broadband fluorescence source in low-coherence interferometry and other applications
in the near-infrared wavelength range.
PACS 42.70.Hj; 42.79.Gn; 42.30.Wb 相似文献
11.
T. Minamisono T. Ohtsubo Y. Nakayama T. Araki K. Mashitani K. Matsuda E. Takahashi M. Tanigaki Y. Someda M. Tanaka A. Kitagawa M. Fukuda K. Matsuta Y. Nojiri 《Hyperfine Interactions》1992,73(3-4):347-356
Hyperfine interactions of β-emitting17F implanted in single crystals of NaF and CaF2 were studied. The nuclear magnetic moment of theT
π=5/2+ state was determined with an improved precision to be |μ(17F;π=5/2+,T
1/2=64.5s|=4.72130±0.00025. nm. Isoscalar magnetic moments of the doubly closed shell ±1 nucleon nuclei around mass number 16
were derived and the effective nucleon mass in the nucleus was discussed. 相似文献
12.
Na2 excited from the X1Σg+ state to the A1Σu+ state by a narrow band (3 MHz) Rhodamine-6G dye laser at 6022.3 Å, the same wavelength at which Na undergoes the 3s–5s two-photon transition, gives four fluorescence series from A1Σu+ levels (v′ = 21, J′ = 26), (18, 33), (33, 19), and (34, 50). The last two series are much weaker in intensity, and at long wavelengths many doublets are lost in the background noise. The same (34, 50) fluorescence series was found by other workers in the lab using a Kr+ (5682 Å) laser as excitation source. Their analysis agrees very well with the findings in the work. 相似文献
13.
A. Qayyum M.N. Akhtar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):181-184
Light emission during sputtering of graphite targets with 1–10 keV Ne+, Kr+ and Xe+ beams has been investigated in the 180-600 nm wavelength range. Beside the characteristic lines of sputtered C1 and C1
+, a continuum superimposed with a number of broad structures was observed in the 250-520 nm range, and having a maximum at
386 nm. Mass analysis of the sputtered flux confirmed the presence of negative carbon clusters C
m
-
, C2
- being the dominant one. Ion beam parameters i.e. ion mass, energy, current density and ion dose were varied to identify the origin of the continuum emission. On the basis
of the experimental results, it is suggested that the continuum is predominantly due to the overlapping of various band systems
of sputtered C2 with a small contribution from the heavier sputtered carbon clusters Cm (m>2).
Received 24 September 1999 and Received in final form 11 February 2000 相似文献
14.
S. Barth P. Birrer F. N. Gygax B. Hitti E. Lippelt A. Schenck 《Hyperfine Interactions》1989,51(1-4):881-890
A series of single crystalline Bi1−x
Sb
x
alloys (x=0,0.03, 0.14, 0.19, 0.37) covering both the semimetallic (0≤x≤0.07 orx≥0.22) and the semiconducting region (0.07≤x≤0.22) was examined using the stroboscopic μ+ SR method. The μ+ Knight shift, negative for all Sb concentrations, shows pronounced temperature dependences and large anisotropies. A scaling
with the-negative-total magnetic susceptibility [1] is found in the semiconducting alloys. In detail, the isotropic part of
the μ+ Knight shift is proportional to the isotropic part of the susceptibility, and the anisotropic Knight shift scales with the
anisotropic susceptibility. Possible mechanisms leading to this relation are investigated. 相似文献
15.
We report on the experimental study of the excitation mechanism of fluorescence in a 10000-ppm wt. Tm+3-doped ZBLAN fiber. Visible (at 453 nm and 480 nm) and near-infrared (∼800 nm) radiations were studied under excitation at
1.064 μm. The up-conversion mechanisms responsible are investigated, based on experimental data. The results show that the3
H
4 and the 1
D
2 levels are predominantly excited by ion-ion cross-relaxation processes.
Received: 19 August 2002 / Published online: 8 January 2003
RID="*"
ID="*"Corresponding author. Fax: +41/31-631-3765, E-mail: Reda.El-Agmy@iap.unibe.ch 相似文献
16.
Dongyu Li Yuxiao Wang Xueru Zhang Kun Yang Lu Liu Yinglin Song 《Optics Communications》2012,285(7):1925-1928
An analysis of the intense blue upconversion emission at 476 and 488 nm in Tm3 +/Yb3 + codoped Y2O3 under excitation power density of 86.7 W/cm2 available from a diode laser emitting at 976 nm, has been undertaken. Fluorescence intensity ratio (FIR) variation of temperature-sensitive blue upconversion emission at 476 and 488 nm in this material was recorded in the temperature range from 303 to 753 K. The maximum sensitivity derived from the FIR technique of the blue upconversion emission is approximately 0.0035 K? 1. The results imply that Tm3 +/Yb3 + codoped Y2O3 is a potential candidate for the optical temperature sensor. 相似文献
17.
The fluorescence from Yb+ ions trapped in an rf trap was detected by driving the2S1/2−2P1/2 transition at 369.52 nm with the radiation generated by sum-frequency mixing of diode-laser and argon-ion-laser radiation.
The rf resonance absorption signal as well as the fluorescence signal, when the Yb+ ions were continuously irradiated by the resonant uv radiation, faded out with a decay time shorter than the storage time.
This observation suggests that the Yb+ ions disappeared from the trap with the irradiation of the resonant uv radiation. 相似文献
18.
Quenching of fluorescence from Na(32
P) and K(42
P) atoms by various collision partners was studied at 973 and 1273K. Excited alkali atoms were produced photolytically by excimer
laser light at 193nm. For each collision pair, the appropriate relative velocity was computed and used to evaluate the quenching
cross-section from the measured rate constants. Cross sections for CO2, O2 and N2 are large (10–60Å2) while for Ar, the values are <1 Å2. The results are compared with those of previous investigations as a function of relative velocity. Finally, implications
for combustion diagnostics are briefly discussed.
Received: 29 March 1996 相似文献
19.
D. Zhang X. Chen Y. Jin X. Cao D. Zhu Y. Wang G. Ding Y. Cui C. Chen Z. Wu G. Lan 《Applied Physics A: Materials Science & Processing》2001,72(1):95-102
Raman spectra of Er:LiNbO3 crystal and Ti-diffusedEr:LiNbO3 strip waveguide, in which the Li/Nb ratio was altered using a vapor-phase equilibration (VPE) technique, were measured at
room temperature in the wave-number range 50–3500 cm-1. Both 488 and 514.5 nm radiations were used to excite Raman scattering, A1(TO) and E(TO) modes were recorded at backward scattering geometry. The results indicated that the lattice vibrational spectra
of the as-grown Er:LiNbO3 are almost the same as those of pure LiNbO3 except for the little shift of the peak position and the change of relative intensity of some peaks. In comparison with the
spectra of as-grown Er:LiNbO3 crystal the vapor-phase equilibrated Er:LiNbO3 and Er:Ti:LiNbO3 crystals in the lattice vibrational region exhibit the following features: firstly, Raman peaks become narrow, indicating
that the VPE process has brought Er:LiNbO3 and Er:Ti:LiNbO3 crystals closer to a stoichiometric composition; secondly, relative intensity of some peaks varies with the VPE time; and
finally, slight blue shifting in peak position was observed. Some of these features were correlated with the NbO6 octahedra and with the site distribution of the doped Er ions. In addition, green fluorescence peaks and/or bands associated
with the electron transitions 2
H
11/2?4
I
15/2 and 4
S
3/2?4
I
15/2 of the doped Er3+ were also observed. For 488 nm excitation they appear in the wavenumber range of 1200–3000 cm-1 and are well separated from lattice vibrational region; for 514.5 nm excitation, however, these fluorescence peaks shift
towards the low wavenumber region and overlap partially with the lattice vibrational spectra.
Received: 24 May 2000 / Accepted: 29 May 2000 / Published online: 13 September 2000 相似文献
20.
Putcha Venkateswarlu 《Hyperfine Interactions》1985,24(1-4):203-221
The infrared and millimeter wave spectroscopy, laser Stark spectroscopy, and beam maser spectroscopy of CH3CN and its isotopic species will be discussed. The beam maser spectroscopy and hyperfine structure of molecules like NCCCD,
ClCCD and CH3CCH are reviewed. The laser magnetic resonance and hyperfine structure in CF, CH and CH2 free radicals will be discussed. The Lamb dip spectroscopy and laser-induced fluorescence in I2 involving theB
3Π(0
u
+
) state are reviewed with special reference to its hyperfine structure. The splitting of the rotational levels of N
2
+
in itsX
2Σ
g
+
andB
2Σ
u
+
states due to hyperfine interactions (along with the hyperfine structure) in laser-induced fluorescence in theB−X transition is discussed. Recent results obtained in the laser photo-acoustic spectrum of ICl in the transitionX
1Σ+ −A
3Π1 will be presented and the possibility of the use of this technique in studying the hyperfine structure will be discussed. 相似文献