共查询到20条相似文献,搜索用时 31 毫秒
1.
I. Sherstov S. Liu Ch. Lisdat H. Schnatz S. Jung H. Knöckel E. Tiemann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(3):485-492
Absolute transition frequencies of the b 3Π(0u
+) - X 1Σg
+ system of K2 were measured in a molecular beam with Lamb dip absorption spectroscopy applying a frequency comb from a femtosecond pulsed
laser. Both, K atoms and K2 molecules are present in the beam and are expected to interact by collisions. The atoms can be deflected optically out of
the beam, and thus the collision rate between K atoms and K2 molecules is changed by about an order of magnitude. The molecular transition frequencies for low collisional rate are compared
with those for high one. Limits for the collisional frequency shift within the beam are determined. 相似文献
2.
Photoelectron angular distributions (PADs) from above-threshold ionization of O2 and N2 molecules irradiated by a bichromatic laser field of circular polarization are studied. The bichromatic laser field is specially modulated such that it can be used to mimic a sequence of one-cycle laser pulses. The PADs are greatly affected by the molecular alignment, the symmetry of the initial electronic distribution, and the carrier-envelope phase of the laser pulses. Generally, the PADs do not show any symmetry, and become symmetric about an axis only when the symmetric axis of laser field coincides with the symmetric axis of molecules. This study shows that the few-cycle laser pulses can be used to steer the photoelectrons and perform the selective ionization of molecules. 相似文献
3.
P. Jasik J. Wilczyński J. E. Sienkiewicz 《The European physical journal. Special topics》2007,144(1):85-91
We report adiabatic potential energy curves of the
Li2
+ molecule. Our curves are tabulated according to
internuclear distance from 2 a0 to 100 a0. We
compare our theoretical results with the ones calculated by other
authors and potential energy curves derived from experiments. For
the ground state and 17 excited states we calculate spectroscopic
parameters and compare them with parameters obtained by other
authors. For the first time we present three new minima for
32Σu
+, 42Σu
+ and 22Πg
excited states. In our approach we use the configuration interaction
method where only the valence electrons of Li atoms are treated
explicitly. The core electrons are represented by pseudopotential.
All calculations are performed by means of MOLPRO program package. 相似文献
4.
K.?Koyasu M.?Niemietz W.?Westh?user G.?Gantef?r 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(1):59-62
The decay path of an Ag8(O2)- cluster photoexcited by a 3.1 eV photon is elucidated using time-resolved photoelectron spectroscopy. Photoabsorption results
in the formation of an excited state giving rise to a peak in the photoelectron spectra with well-resolved vibrational finestructure.
With a lifetime of about 100 fs this bound state decays into an anti-bonding state which dissociates into O2 and Ag8- on a timescale of 10 ps. In the photoelectron spectra, this corresponds to a broad maximum shifting gradually towards higher
binding energy while the O2 and Ag8- separate. Finally, the spectrum of bare Ag8- appears. This process is unique to small clusters, because on metal surfaces excited state lifetimes are too short to allow
for direct dissociation. 相似文献
5.
V. N. Lokhman D. D. Ogurok E. A. Ryabov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(1):59-67
We report about effective ionization of iodine atoms and CF3I molecules under the action of intense XeCl laser radiation (308 nm). The only ion fragment resulting from the irradiation
of the CF3I molecules is the I+ ion. We have studied the influence of the intensity, spectral composition, and polarization of the laser radiation used on
the intensity
of the ion signal and the shape of its time-of-flight peak. Based on the
analysis of the results obtained, we have suggested the mechanism of this
effect. The conclusion drawn is that the ionization of the iodine atoms by
the ordinary XeCl laser with a nonselective cavity results from a three- (2 + 1)-photon REMPI process. This process is in
turn due to the presence of accidental two-photon resonances between various spectral components of the laser radiation and
the corresponding intermediate excited states of the iodine atom. The probability of ionization of the atoms from their ground
state I(2P3/2) by the radiation of the ordinary XeCl laser is more than two orders of magnitude higher than the probability of their ionization
from the metastable state I*(2P1/2). The ionization of the CF3I molecules by the XeCl laser radiation occurs as a result of a four-photon process involving the preliminary one-photon dissociation
of these molecules and the subsequent (2 + 1)-photon REMPI of the resultant neutral iodine atoms. 相似文献
6.
A miniature tunable TEA CO2 laser using isotope 13C16O2 as the active medium is developed to extend the spectral range of CO2 lasers for further application. The optimization of the energy parameters of the tunable TEA 13C16O2 laser and the same laser using 12C16O2 are studied. When a gas mixture (13C16O2: N2: He = 1: 1: 3) at a total pressure of 6.4 × 104 Pa is used, the TEA 13C16O2 laser of a 45-cm3 active volume obtains 51 emission lines in the [0001–1000] and [0001–0200] bands. The maximum pulse energy of the TEA 13C16O2 laser is about 357 mJ. The same laser using the conventional gas mixture (12C16O2: N2: He = 1: 1: 3) at a pressure of 6.66 × 104 Pa is measured to obtain 69 laser emission lines and the maximum pulse energy of laser radiation is about 409 mJ. 相似文献
7.
M. A. Kalyar S. Mahmood S.-U. Haq N. Amin M. A. Baig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):229-236
We report a systematic line shape analysis study of the 6p7p configuration
based 1P1, 3D1 and 3P1 autoionizing
resonances in barium using a Nd:YAG pumped dye laser system in conjunction
with a thermionic diode ion detector. The even parity isolated autoionizing
resonances have been approached via four intermediate states 6 snp
1P1 (6 ≤n ≤8) and 5d6p 1P1. A comparison of
the Fano parameters of the resonance profiles reveals that the width of an
autoionizing resonance is independent of the excitation path while the line
profile parameter changes with the selection of different intermediate
states. 相似文献
8.
Mohamed A. Mahmoud 《Central European Journal of Physics》2008,6(3):530-538
We have studied the formation of the molecular ion Rb2+ and the atomic ion Rb+. These are created in laser excited rubidium vapor at the first resonance, 5s–5p and 5p-nl transitions. A theoretical model
is applied to this interaction to explain the time evolution and the laser-power dependence of the population density of Rb+ and Rb2+. A set of rate equations which describe: the temporal variation of the population density of the excited states; the atomic
ion density; and the electron density, were solved numerically under the experimental conditions of Barbier and Cheret. In
their experiment the Rb concentration was 1×1013cm−3 and the laser power was taken to be 50–500 mW at vapor temperature = 450 K. The results showed that the main processes for
producing Rb2+ are associative ionization and Hornbeck-Molnar ionization. The calculations have also showed that, the atomic ions Rb+ are formed through the Penning Ionization (PI) and photoionization processes. Moreover, a reasonable agreement between the
experimental results and our calculations for the ion currents of the Rb+ and Rb2+ is obtained.
相似文献
9.
A. Merli F. Sauer L. Wöste A. Lindinger 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):217-220
We report on isotope selective three-photon ionization of
two isotopomers of KRb by applying evolution strategies. The
particularity of this experiment is based on the high resolution
phase and amplitude modulation of the fs-laser pulses provided by a
2 × 640 pixel pulse shaper. The optimization in a closed feedback
loop performed with spectrally broad pulses centered at 840 nm shows
high enhancements of one isotopomer at the expense of the other
isotopomer and vice versa. From the optimal laser field we aim to
gain details about the selective ionization sequence and the
wavepacket evolution on the involved vibrational states. 相似文献
10.
N. Coluccelli G. Galzerano L. Bonelli A. Toncelli A. Di Lieto M. Tonelli P. Laporta 《Applied physics. B, Lasers and optics》2008,92(4):519-523
We present a comparative analysis on the growth, the spectroscopic features, and the cw laser action of room-temperature Yb(5%):LiYF4 (YLF) and Yb(10%):KYF4 (KYF) crystals. Optical slope efficiencies of 33% and 52% have been demonstrated for Yb:YLF and Yb:KYF crystals, respectively.
A remarkable wide wavelength tunability from 1.01 to 1.07 μm has been obtained for both laser crystals. 相似文献
11.
A. V. Burenin 《Optics and Spectroscopy》2010,108(4):506-511
The internal dynamics of the isotopically asymmetric ionic complexes ArH2D+ and ArD2H+ is considered to be a distorted dynamics of the isotopically symmetric ArH3+ complex. By using the group chain methods, a rigorous algebraic model is constructed to describe the spectrum of the asymmetric
complexes with an allowance for the torsional motion of the structure of hydrogen nuclei. The model is based on the geometrical
group of symmetry of internal dynamics of the isotopically symmetric ionic complex, which is used here as a noninvariant group. 相似文献
12.
We report spectroscopic and laser properties for propagation directions outside the principal axes of Yb3+-doped low symmetry laser crystals with a special devotion to the wavelength dependence anisotropy. We illustrate our report
with experimental data in the 900–1075 nm range of wavelengths from the Yb3+:La2CaB10O19 monoclinic crystal excited under laser diode pumping at 975 nm. This study, which makes easier the realization of Yb3+ lasers with an efficient free-running operation at the wavelength having the highest emission intensity or at a specified
wavelength, or emitting two frequencies with a specified frequency difference, is of promising interest for applications. 相似文献
13.
P. Camy J.L. Doualan A. Benayad M. von Edlinger V. Ménard R. Moncorgé 《Applied physics. B, Lasers and optics》2007,89(4):539-542
We present the spectroscopic properties and room-temperature cw tunable laser operation of Yb3+-doped CaF2, SrF2 and BaF2 single crystals grown and studied in the same conditions. Emission cross sections, lifetimes, laser thresholds, laser slope
efficiencies and laser wavelength tuning ranges are compared. It appears that Yb3+-doped BaF2 might be more promising for diode-pumped high power laser operation.
PACS 42.55.Rz; 42.70.Hj 相似文献
14.
The absorption spectra, fluorescence spectrum and fluorescence decay curve of Nd3+ ions in CaNb2O6 crystal were measured at room temperature. The peak absorption cross section was calculated to be 6.202×10−20 cm2 with a broad FWHM of 7 nm at 808 nm for E//a light polarization. The spectroscopic parameters of Nd3+ ions in CaNb2O6 crystal have been investigated based on Judd-Ofelt theory. The parameters of the line strengths Ω
t
are Ω
2=5.321×10−20 cm2,Ω
4=1.734×10−20 cm2,Ω
6=2.889×10−20 cm2. The radiative lifetime, the fluorescence lifetime and the quantum efficiency are 167 μs, 152 μs and 91%, respectively. The fluorescence branch ratios are calculated to be β
1=36.03%,β
2=52.29%,β
3=11.15%,β
4=0.533%. The emission cross section at 1062 nm is 9.87×10−20 cm2. 相似文献
15.
Bin Dong BaoSheng Cao ZhiQing Feng XingJun Wang ChengRen Li RuiNian Hua 《中国科学G辑(英文版)》2009,52(7):1043-1046
The Er3+-Yb3+ codoped Al2O3 nanoparticles with an average particle size of about 50 nm have been synthesized by an arc discharge synthesis method. The
green and red up-conversion emissions centered at about 526, 547 and 677 nm, corresponding respectively to the 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3+, were detected by a 978-nm semiconductor laser diode excitation. The Annealing has evident effect on the up-conversion emissions
of the samples: The red up-conversion emission is noticeable before annealing; however, the green up-conversion emission becomes
predominant after annealing. The mixture of (Er,Yb)3Al5O12 and α-(Al,Er,Yb)2O3 phases is more favorable for green up-conversion emissions due to an enhancement of the ESA (I) of 4I11/2+a photon→4F7/2 and ET (III) of 2F5/2(Yb3+)+4I11/2(Er3+)→2F7/2(Yb3+)+4F7/2(Er3+) processes. The two-photon absorption up-conversion process is involved in the green and red up-conversion emissions. The
results have proved that arc discharge synthesis is a new promising preparation technology for optical materials.
Supported by National Natural Science Foundation of China (Grant No. 10804015), the Scientific Research Foundation for Doctor
of Liaoning Province (Grant No. 20071095), and the Educational Committee Foundation of Liaoning Province (Grant No. 2008123) 相似文献
16.
M. Niemietz M. Engelke Y.D. Kim G. Ganteför 《Applied Physics A: Materials Science & Processing》2007,87(4):615-619
We present time-resolved photoelectron spectra of mass-selected Ag2O2 anions. The anions are photoexcited by photons with an energy of 3.1 eV, and photoelectron spectra of the excited species
Ag2O2
-
* and the subsequently appearing fragments are recorded using a probe laser pulse with a photon energy of 1.5 eV. The excited
state of Ag2O2
- has a short lifetime of 130 fs±70 fs only and decays by direct photodesorption of O2. The data demonstrate the ability of time-resolved photoelectron spectroscopy (TR-PES) to observe the breaking of chemical
bonds if the decay process of the excited state is direct (non-thermal desorption). The data are compared to recent results
of a NeNePo experiment [1] on the same system.
PACS 68.43.Tj; 78.47.+p; 33.80.Eh; 36.40.-c 相似文献
17.
Nd3+:NaY(WO4)2, known as Nd:NYW, is a new type crystal. By using laser-diode as pump source, a passive Q-switching of intracavity-frequency-doubling Nd:NYW/KTP laser has been realized with Cr4+:YAG saturable absorber. The dependence of pulse repetition rate, pulse energy, pulse width, and peak power on incident pump power for different small-signal transmissions of Cr4+:YAG are measured. The coupled rate equations are used to simulate the Q-switched process of laser, and the numerical solutions agree with the experimental results. 相似文献
18.
Tingyin Ning Cong Chen Yueliang Zhou Heng Lu Dongxiang Zhang Hai Ming Guozhen Yang 《Applied Physics A: Materials Science & Processing》2009,94(3):567-570
CaCu3Ti4O12 (CCTO) thin films were successfully prepared on LaAlO3 substrates by pulsed laser deposition technique. We measured the nonlinear optical susceptibility of the thin films using
Z-scan method at a wavelength of 532 nm with pulse durations of 25 ps and 7 ns. The large values of the third-order nonlinear
optical susceptibility, χ
(3), of the CCTO film were obtained to be 2.79×10−8 esu and 3.30×10−6 esu in picosecond and nanosecond time regimes, respectively, which are among the best results of some representative nonlinear
optical materials. The origin of optical nonlinearity of CCTO films was discussed. The results indicate that the CCTO films
on LaAlO3 substrates are promising candidate materials for applications in nonlinear optical devices. 相似文献
19.
Vacuum ultraviolet luminescence of Er3+ ions in LiYF4 and BaY2F8 crystals has been investigated. It is revealed that under excitation by 193 nm radiation from an ArF excimer laser the interconfigurational 5d–4f radiative transitions in Er3+ ions are observed. It is shown that from the LiYF4:Er crystal only the spin-forbidden luminescence (λ = 165 nm) is detected, whereas both the spin-forbidden (λ = 169 nm) and spin-allowed (λ = 160.5 nm) components are observed from the BaY2F8:Er crystal. 相似文献
20.
We measured the absorption and luminescence spectra of Nd3+ ions in an inorganic solvent POCl3-BCl3. The spectra were analyzed in terms of the Judd-Ofelt theory. We calculated the Judd-Ofelt parameters, oscillator strengths,
spontaneous emission probabilities, luminescence quantum yield, and the stimulated emission cross section for the laser transition
4
F
3/2 → 4
I
11/2 of the neodymium ion in a POCl3-BCl3-Nd3+ solution. 相似文献