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1.
A. Ghoshal P. Mandal 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(2):327-335
e+ + H(ns) ↦e+ + H(n′s) transitions for arbitrary n and
n′ have been studied using the distorted-wave formalism in the
momentum space [Ghoshal and Mandal, Phys. Rev. A 72, 032714 (2005)]. The distorted-wave
scattering amplitudes have been written in a simple closed analytical form. A detailed
study has been made on differential and total cross sections in the energy range 20–300 eV.
Resonance-like behaviour of the
differential cross section has been observed in the the region of lower scattering angles
for high Rydberg transitions. To the best of our knowledge the distorted-wave results for
differential and total cross sections for such arbitrary transitions are reported for the
first time in the literature. 相似文献
2.
3.
Leif Holmlid 《Journal of nanoparticle research》2011,13(10):5535-5546
The inter-atomic distances in potassium clusters of Rydberg matter (RM) at excitation levels n
B = 4–8 were recently measured by phase-delay spectroscopy (Holmlid, J Nanopart Res 12: 273, 2010). Excitation levels n
B < 4 with shorter inter-atomic distances exist for hydrogen clusters, and distances down to 140 pm are now measured with this
light-scattering method. The clusters studied have maximum dimensions from 0.3 nm up to several tens of nm, often being planar.
A weak carbon dioxide laser beam interacts with the clusters in a tunable RM cavity. A strong fringe structure is observed
as a function of the end-grating angular position. Delay lengths in the clusters are derived from the fringe structure, corresponding
to twice the distance between rows or planes in the clusters. Good agreement with predicted and a few previously measured
distances in excitation levels n
B = 1, 2, and 3 is found. Close-packing is the main structure both in planar and 3D clusters. Planar clusters are only observed
for n
B = 1 and 3, while 3D clusters are found in excitation levels n
B = 1, 2 and 3. The cluster–cluster distance in stacks of planar clusters for n
B = 2 and 3 is now observed for the first time. 相似文献
4.
Leif Holmlid 《Journal of nanoparticle research》2010,12(1):273-284
Recently, rotational spectroscopy in the radio frequency range was used to determine the bond lengths in several types of
potassium Rydberg Matter (RM) clusters with high precision (Mol Phy 105: 933–939, 2007). Due to the large bond lengths of
a few nm and well-ordered structure of such clusters, it is expected that light scattering can be used to determine their
dimensions. A weak carbon dioxide laser beam is introduced collinearly into a tunable RM cavity. When RM is formed, a very
pronounced fringe structure with several hundred fringes is observed at the detector as a function of the grating position.
These fringes show a phase delay of the carbon dioxide laser light caused by reflections within the RM clusters. The delay
lengths derived from the fringe structure give distances between the rows of atoms in the clusters. The excitation level of
the most easily observed clusters is n = 5. Clusters with n = 6, 7, and 8 are also commonly detected. The bond distance for n = 5 is found to be 3.804 ± 0.015 nm, while that for n = 6 is 5.525 ± 0.014 nm, in accurate agreement with values from rotational spectroscopy. 相似文献
5.
The luminescence properties of Re(I) complexes incorporating the dcbpy ligand (dcbpy = n,n′-dicarboxylic acid-2,2′-bipyridine; n = 3, 4) were investigated as well as their utility as Pb2+ sensors. An unusual binuclear complex of the 3,3′- species was isolated. The emission intensity and lifetime for all complexes
were found to be highly temperature-dependent, with quantum yields and lifetimes dramatically greater at 77 K than at room
temperature. The monomeric 3,3′-dcbpy Re(I) complex demonstrates nearly 1:1 binding with Pb2+. The effect of this lead binding on the emission intensity is great, but the low quantum yields allow only for detection
of the metal at the micromolar level. The binding of Pb2+ to the 4,4′-dcbpy complex is modeled and the interaction is demonstrated to involve two binding sites. 相似文献
6.
The influence of neutral species in the E- and D-layers of the Earth’s upper atmosphere on the spectrum of the spontaneous emission (absorption) of Rydberg atoms and molecules
for transitions that occur without changing the principal quantum number (Δn = 0) is examined. Along with the process of l-mixing, the splitting of orbitally degenerate states due to interaction with perturbing neutral species of the medium is
taken into account. The possible types of radiative transitions between them are analyzed. It is demonstrated that, for principal
quantum numbers of n = 10–30, decimeter-band radiation corresponds to transitions between the levels of split states, whereas meter-band radiation,
to transitions between their individual components. It is established that, for these values of n, the ratios of the intensities of the decimeter and meter bands for Δn = 0 transitions to the intensity of IR radiation (Δn = 1) are 10−4 and 10−6, respectively. The issue of satellite signal phase shift because of multiple Raman scattering in the D-layer of the atmosphere is discussed. 相似文献
7.
Y. Zhang C. Y. Chen M. Huang Y. S. Wang Y. M. Zou 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,56(2):157-166
Ab initio calculations of the total dielectronic
recombination (DR) rate coefficients for thirteen ions along the NiI
isoelectronic sequence in the ground state (Kr8+, Mo14+,
Ag19+, Sn22+, Xe26+, Nd32+, Gd36+,
Yb42+, W46+, Au51+, Pb54+, At57+, and
U64+) have been performed using the flexible atomic code. The
level-by-level calculations are performed for evaluating the DR
contributions through the relevant Cu-like autoionizing inner-shell
excited 3l174l′n′′l′′ and 3l175l′n′′l′′ configuration complexes with n′′
≤15, which are associated with Δn=1 and Δn=2
core-excitations, respectively. The usual (n′′)-3 scaling
law is found to be invalid for low-Z ions. A level-by-level
extrapolation procedure is employed to obtain the contributions
through higher n′′ complexes. The decays to autoionizing
levels followed possibly by radiative cascades could enlarge the
rates at relatively high temperature by a factor up to about 23%.
For the whole isoelectronic ions the contributions from
3s23p63d9 4l′n′′l′′ dominate the total DR
rates while the contributions from the 3s23p63d9 5l′n′′l′′ configuration complexes are about 10-20% at
relatively high temperature. On the basis of the calculated results,
a general analytic formula for the total DR rate coefficients of all
the ions with 36≤Z ≤92 along the NiI isoelectronic
sequence is constructed. The comparisons of the rates obtained from
the general formula with those from the detailed calculations show
that the formula is of high precision, generally better than 3%
accuracy for electron temperatures kT≥0.1EI, where EI is
the ionization energy of the Cu-like ion. The present DR rates at
temperature above 1.0EI are larger than the previously published
data by a factor above 30%. The commonly used semiempirical formula
proposed by Burgess and modified by Merts may overestimate the rates
at high temperature by a factor of about 2 for low-Z ions. 相似文献
8.
General expressions for the probability of all strongly forbidden magnetic-dipole transitions between states njl and n′jl in the hydrogen atom and light hydrogen-like ions are derived in the lowest order in the parameter (αZ) in the form W
n′jl;njl
(Ml) = D
n′n
lj
αm
e
(αZ)10 (in relativistic units), where m
e
is the electron mass, α is the fine-structure constant, Z is the nuclear charge, and the constants D
n′n
lj
are presented in an analytical form. Using these expressions, the dependence of the degree of parity violation on the principal
quantum numbers n and n′ of the lower and upper states in the ns
1/2-n′s
1/2 and np
1/2-n′p
1/2 M1 transitions is systematically analyzed. The results obtained can be used in designing experiments on parity violation
in the hydrogen atom. 相似文献
9.
2 Σ+,H′ 2Π±(v′=2), and 4dσ,πO2Σ+,O′ 2Π±(v′=0) Rydberg states of NO molecules are described. The analyses of the two-photon excitation functions and infrared emission
spectra revealed that only the 2Π- component was involved in PFWM. This is in good accordance with the absence of amplified spontaneous emission (ASE) in the
2Σ+ and 2Π+ components due to their predissociative character. Results provide some support for the mechanism that the generation of
the vacuum ultraviolet radiation was brought by PFWM in which ASE served as a third driving wave.
Received: 6 January 1998 相似文献
10.
Leif Holmlid 《Journal of Raman spectroscopy : JRS》2008,39(10):1364-1374
Recently, rotational spectra of giant Rydberg matter (RM) clusters were studied in the radio frequency range (Mol. Phys. 105 (2007) 933–939), giving high‐precision bond distances in the nanometer range. However, the theoretical and experimental problem of vibrational motion or, rather, coupled electronic‐vibrational motion in the RM clusters is still unsolved; but it is expected that broad phonon bands will exist. Spectroscopic signatures from space make it likely that RM is a common form of matter in the Universe, and phonon bands in this spectroscopic range have not been taken into account so far. Spectroscopic results are now reported on transitions in the range 0.01–20 cm−1, using primarily infrared (IR) lasers to probe the RM in a tunable open cavity with a Fabry–Perot interferometer to aid in the identification of the shifts. Stimulated Raman scattering from electronic transitions and Rabi‐flopping from electronic states in the clusters are observed. The broad stimulated Raman peaks are assigned to one and two consecutive vibrational (electronic‐vibrational) transitions. Theoretical values predicted for vibrations (phonon maxima) and electronic processes are in reasonable agreement with the experimental results. Improved calculations are needed to verify the assignments of the vibrational phonon distributions. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
11.
Shengyi Yang Xiulong Zhang Zhidong Lou Yanbing Hou 《Applied Physics A: Materials Science & Processing》2008,90(3):475-478
In this paper, electroluminescence from organic light-emitting diodes based on 2-(4′-biphenyl)-5-(4′′-tert-butylphenyl)-1,3,4-oxadiazole (PBD) and N,N′-diphenyl-N,N′-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (TPD) is reported. Based on the exciplex emission from the TPD/PBD interface under high electric fields, the influence
of the TPD/PBD interface on exciplex emission was investigated by increasing the number of TPD/PBD interfaces while keeping
both the total thickness of the TPD layer and the PBD layer constant in the multiple quantum-wells (MQW) device ITO/TPD/[PBD/TPD]n/PBD/Al (n is the well number that was varied from 0 to 3). Our experimental data shows that exciplex emission can be enhanced
by suitably increasing the well number of this kind of MQW-like device.
PACS 78.60.Fi; 78.55.Kz; 73.61.Ph 相似文献
12.
The cavity ring down (CRD) technique presented here involves an optical cavity attached to a cryostat. The static cell and
mirrors of the optical cavity are all inside a vacuum chamber at the same temperature of the cryostat. The temperature of
the cell can be changed between 77 K and 298 K. An off-axis alignment of the laser beam into the cavity is used to increase
the number of resonant modes inside the cavity and improve the signal to noise ratio of the absorption bands. To demonstrate
the capabilities of the low temperature CRD cell, the absorption spectra of O2 are recorded at 90 K for the A (υ′=0←υ″=0) and γ (υ′=2←υ″=0) bands of the b1?g +? X3?g -b^{1}\sum_{g}^{ +}\leftarrow X^{3}\sum_{g}^{ -} transition using cavity ring down spectroscopy. The optical cavity performance was tested using two variations of the CRD
technique. The A-band is measured using the phase-shift cavity ring down method and the γ-band using the pulsed-laser exponential-decay method. A comparison between experimental and simulated spectra of the O2 bands at 90 K confirms the molecular temperature measured by a sensor localized in the cell. Quantitative measurements of
the individual rotational line intensities are made for the oxygen γ-band to confirm the temperature of the cell and calculate the vibrational band intensity. The application of this technique
for laboratory studies of planetary atmospheres and the spectroscopy of molecular complexes is emphasized. 相似文献
13.
General properties were determined and asymptotic approximation formulas for probabilities of spontaneous decay and photoionization
cross-sections were derived on the basis of numerically calculated amplitudes of bound-bound and bound-free radiation transitions
from Rydberg nS-, nP- and nD-states of alkali atoms with high principal quantum numbers, up to n = 1000. The departure of data from the asymptotic formulas for states with principal quantum numbers in the range between
n = 10 and n = 2000 from originally calculated data does not exceed 0.1–1%, and may be useful for estimations of natural radiation widths
for arbitrary high Rydberg levels. 相似文献
14.
Multiphonon ionization of the H2 molecule under the action of a weak (probe) field, which provides the initial population of the low-lying (working) level,
and intense monochromatic linearly polarized radiation is studied. The multiphoton ionization process occurs under the conditions
of strong field perturbation of two intermediate Rydberg series, np0(1Σ
u
+
and np2(1Πu), of the optical R(0)branch which have different ionization potentials. The series are occupied simultaneously as a result of single-photon
absorption by an excited H
2
*
molecule in the working state 4s
σH′1Σ
g
+
(v=0). As a result of the irregularity in the arrangement of the intermediate levels from a large group of states that are combined
in the multiphoton ionization process a sharp and irregular change occurs in the dependence of the shifts and widths Γn of the levels on the intensity f of the strong field in a transition from one level to another. It is shown that for field intensities f such that the level widths remain much less than the splitting between the levels (Γn≪/n
3) the stabilizing effect (i.e., the field-induced narrowing of the levels as f→∞) in the form Γn ∝ 1/f
2 (as happens in atoms with a structureless core) is not observed in molecular systems.
Zh. éksp. Teor. Fiz. 115, 1987–2000 (June 1999) 相似文献
15.
In the context, a modified sol-gel technology was afford to the synthesis of rare earth composite ceramic phosphors MM′O3/CeO2 and MM′O3/CeO2: Pr3+ (M = Ca, Sr; M′ = Ti, Zr) with multicomponent hybrid precursors were composed. The micromorphology, particle size and photoluminescence
properties were studied with XRD, SEM and luminescent spectroscopy in detail. Both XRD and SEM indicated the particle sizes
were in the submicrometer range of 100 ∼ 300 nm. The photoluminescence for these ceramic phosphors were studied in details
with the different component of host (molecular ratio of Sr, Ca and Ti, Zr), presenting a broad spectral band in the visible
blue-violet region with the maximum excitation peak at 449 nm and a wide emission range with a maximum peak at 619 nm, which
was ascribed to be the characteristic transition of Pr3+ (1D2 → 3H4). These phosphors can be expected for visible light conversion (blue → red) materials. Especially it can be found that the
introduction of CeO2 can enhance the luminescence intensity of MM′O3 and MM′O3: Pr3+. 相似文献
16.
The autoionization mechanisms of dense nP3/2 (n = 20–97) Rydberg gases of 87Rb atoms in the spontaneous evolution were investigated for the first time. By observing the characteristic time of the electrons generated through autoionization process, the dependence of autoionization mechanisms (black-body radiation, electron–Rydberg collision, and Penning ionization) on the principal quantum number n of initial nP states was demonstrated. The dependence on the number n in nP Rydberg atoms is similar to those in nD Rydberg atoms. 相似文献
17.
S. Hayashi T. Suzuki T. Ichimura K. Tsukiyama 《Applied physics. B, Lasers and optics》1997,65(4-5):555-561
2 Σ+,H′2Π(v′=0)←X2Π(v′′=0) two-photon transition of NO, both near-infrared and vacuum ultraviolet radiation were emitted along the laser propagation
direction. The analyses of emission and excitation spectra revealed that the parametric four-wave mixing (PFWM) process coexisted
with amplified spontaneous emission. Polarization properties of the IR radiation are found to be dependent on the rotational
levels. Pressure and laser power behaviors of the generated waves were reported. The mechanism of PFWM was discussed in terms
of selection rules of the relevant ro-vibronic transitions.
Received: 19 September 1996/Revised version: 27 January 1997 相似文献
18.
Karamjit Singh Sunil Kumar N. K. Verma H. S. Bhatti 《Journal of nanoparticle research》2009,11(4):1017-1021
Eu3+-doped Cd1−x
Zn
x
S (0 ≤ x ≤ 0.5) quantum dots (QDs) have been synthesized using wet chemical precipitation method. X-ray diffraction and transmission
electron microscope have been used for the crystallographic and morphological characterization of synthesized nanomaterials.
In order to understand the spectral characteristics of doped QDs, N2-laser induced time resolved spectra have been recorded. Excited state lifetime values for dichromatic emission (red and violet)
attributed to 5D0 → 7FJ (J = 1, 2) transitions of Eu3+ and host lattice transitions have been calculated from the recorded luminescence decay curves. Decay time dependence on the
dopant concentration (0.01–10 at. wt% of Cd2+) has been studied in detail. 相似文献
19.
We demonstrate a three-step laser stabilization scheme for excitation to nP and nF Rydberg states in 85Rb, with all three lasers stabilized using active feedback to independent Rb vapor cells. The setup allows stabilization to
the Rydberg states 36P3/2–70P3/2 and 33F7/2–90F7/2, with the only limiting factor being the available third step laser power. We study the scheme by monitoring the three laser
frequencies simultaneously against a self-referenced optical frequency comb. The third step laser, locked to the Rydberg transition,
displays an Allan deviation of 30 kHz over 1 second and <80 kHz over 1 hour. The scheme is very robust and affordable, and
it would be ideal for carrying out a range of quantum information experiments. 相似文献
20.
Two-photon Rydberg resonances in lithium-7 obtained by recording reduction of resonance fluorescence
In a magneto-optical trap (MOT) of 7Li, two-photon Rydberg resonances are recorded by using a spectroscopic technique, which based on variation in the resonance fluorescence. The first excitation frequency is detuned by 0.59 GHz from the intermediate 2P 3/2 state. Two counter-propagating laser beams are used. The resonances are studied on two-photon transitions 2S 1/2 ? nl in a range of principal quantum number n from 38 to 120. The widths of the observed resonances are varied from 4.4 to 13 MHz for different MOT parameters. 相似文献