里德堡钾原子的布居数在受激拉曼绝热通道中的相干迁移

本文用含时多态展开方法研究了在两束部分重叠的脉冲场驱动下布居数在钾原子量子态中的相干迁移。结果表明，布居数能否实现完全迁移取决于两个脉冲的持续时间和重叠程度，当脉冲的持续时间和重叠合适时，将发生布居数的完全迁移，并形成布居数囚禁。     

Dipole‐like backscatter stimulated Raman scattering for in vivo imaging

Stimulated Raman scattering (SRS) scanning microscopy has the potential to enable label‐free in vivo imaging for research and clinical medicine. Volume SRS from focus occurs in the forward scattered direction. Therefore, multiple scattering events are required to direct the light out of the tissue, reducing imaging depth and resolution. Here, a method called Stokes interference SRS (SISRS) is introduced that operates by the addition to the standard pump and stimulated emission probe beams a third beam called the donut beam. The donut is close in wavelength to the probe beam and, after passage through a π phase plate, forms an annular beam in the focal plane with bright nodes above and below focus. The donut beats with the probe beam, and when they destructively interfere with each other, the microscope's 3‐D stimulated emission focal spot is reduced to subwavelength dimensions. A subwavelength focal volume emits a dipole pattern of SRS with forward and backscatter lobes, enabling high‐resolution single‐backscatter imaging from deep within tissues. The reduction of the focal volume also increases the resolution of the scanning image creating imaging beyond the diffraction limit. SISRS imaging may provide in vivo label‐free Raman images comparable with that achieved in stained in vitro tissues in all planes of section. Copyright © 2014 John Wiley & Sons, Ltd.     

Structural phase transitions in loparite‐(Ce): evidences from Raman light scattering

Raman spectroscopic studies of loparite‐(Ce), a mineral of the perovskite family, are presented. Polarized Raman spectra were obtained in the temperature range of 50–300 K. As analysis of the behavior of Raman modes showed, the temperature dependences of wavenumber, damping and intensity of the optical modes exhibited anomalies near 220 and 150 K. Softening of the low‐wavenumber modes observed in the vicinity of 150 K is interpreted as an evidence of a ferroelectric phase transition. An anisotropic quasielastic light scattering in the low‐wavenumber region of the Raman spectra was observed from 300 to 150 K. As the data suggest, loparite‐(Ce) has two structural phase transitions, one of which (at 150 K) is a ferroelectric transition of the order–disorder type. Copyright © 2014 John Wiley & Sons, Ltd.     

Temperature measurements in condensed phases using non‐resonant femtosecond stimulated Raman scattering

We have previously demonstrated the capability of femtosecond stimulated Raman scattering (FSRS) data to measure the temperature (T) of condensed matter at the molecular vibrational level. [Phys. Rev. Lett. 2011, 107, 43001] In this paper, we expand the theory for the FSRS temperature dependence by considering the effects of an isolated change of T as well as a coupled change of T and chemical concentration. We point out that the origin of the temperature sensitivity of the Stokes to anti‐Stokes ratio of FSRS lies in the exponential nonlinearity of the gain and loss. We establish that FSRS of two Raman modes can be used to simultaneously determine the vibrational temperature and the change in concentration of the species contributing to those two modes. Single‐shot experimental results using FSRS are presented to demonstrate over four orders of magnitude higher efficiency than spontaneous Raman in small volume samples with picosecond resolution. Copyright © 2012 John Wiley & Sons, Ltd.     

Rydberg transitions in neon observed by optogalvanic effect in the 830-870 and 380-420 nm regions

New optogalvanic (OG) Rydberg-Rydberg transitions of neon have been observed in the near-infrared region (830-870 nm), using a commercial Fe-Ne hollow cathode. They involve transitions from the 3d[3/2] J=1 and 3d[7/2] J=3,4 levels to high-lying nf levels. In addition, other OG transitions, observed in the blue range, have been completely assigned to ns, nd, ns′ and nd′ Rydberg series excited from the 3p[1/2] J=1 and 3p[5/2] J=2,3 levels of neon. These transitions and assignments allowed us to extend the range of tunable laser calibration on the two edges of the visible range, where there is a lack of available calibration lines, i.e. the near-infrared and the far-blue range, with a 0.01 nm absolute accuracy.     

Raman study of phase transitions in double orthophosphates of lutetium and potassium

This study by Raman spectrometry of double orthophosphates of lutetium and potassium consists of a systematic analysis of double orthophosphates of the potassium and lanthanide family. In the 10-300 K temperature range three solid-solid phase transitions in this compound are obtained which demonstrate the application of Raman spectrometry to the study of the nature and mechanism of such transitions.     

Frequency comb expansion in a monolithic self‐mode‐locked laser concurrent with stimulated Raman scattering

The discovery of a novel phase‐locked frequency comb generated from a monolithic laser with the concurrent processes of self‐mode locking (SML) and stimulated Raman scattering (SRS) is reported. It is experimentally shown that the width of the Raman gain can be exploited to considerably expand the frequency comb of a monolithic SML crystal laser via the SRS process. At a pump power of 6.5 W, an output power of 140 mW in the Stokes wave with a pulse width as narrow as 2.9 ps at a pulse repetition rate of 6.615 GHz is obtained. The present finding not only provides useful insights into the monolithic intracavity SRS process but also paves the way for generating mode‐locked pulses based on monolithic self‐Raman crystals.     

Spectroscopic,structural and theoretical studies of 2‐methyl‐4‐nitroaniline (MNA) crystal. Electronic transitions in IR

Polarized FT‐IR, Raman, neutron scattering (IINS), and UV‐Vis‐NIR spectra of 2‐methyl‐4‐nitroaniline (MNA) crystal plates, powder, and solutions were measured in the 10–50 000 cm⁻¹ range. The FT‐IR spectrum of deuterated MNA (DMNA) in KBr pellet, the Raman spectrum of the DMNA powder as well as the EPR spectrum of the MNA powder were also recorded. Complete assignments of bands to normal vibrations have been proposed. Density functional theory (DFT) calculations of wavenumbers and potential energy distribution (PED) have been performed to strengthen the assignments. The analysis of vibrational and electronic spectra has revealed vibronic couplings in MNA molecules in solutions and in crystals. In the polarized FT‐IR spectra of the crystal five unusually large bands are observed in MIR and NIR regions. Their origin is discussed in terms of N H···O, C H···O, C H···H N hydrogen bonds, intermolecular charge transfers, electrostatic interactions, and ion radicals formation in the crystal. The role of a methyl group introduction to 4‐nitroaniline is analyzed. The crystal structure of MNA at the room temperature was re‐investigated. Copyright © 2008 John Wiley & Sons, Ltd.     

Lineshape analysis of stimulated Raman spectra of the near‐nozzle region of free jet expansions

An anomalous lineshape of stimulated Raman spectra obtained from the region very close to the nozzle of supersonic pulsed expansions of nitrogen is presented. High‐resolution Raman spectra of the Q branch of the fundamental vibration mode of N₂ have been recorded from two different nitrogen expansions at T₀ = 295 K and P₀ = 1.5–3.5 bar, the lasers crossing the jet axis in the range z/D = 0.25–1.25, where D is the effective nozzle diameter. The combination of Doppler shifts and strong gradients of density and temperature in the near‐nozzle region yield an inhomogeneous broadening and a double peak structure of the recorded Raman line profiles. The comparison of the experimental results with the simulation of the Raman spectrum from this region provides valuable information about the near‐nozzle flow field. The lineshape described here is different from another reported previously in the literature, which is based on a depletion of the density of free molecules on the axis due to condensation. Copyright © 2009 John Wiley & Sons, Ltd.     

High‐resolution stimulated Raman spectroscopy and analysis of the ν1 band of osmium tetroxide

We present the first high‐resolution stimulated Raman study of osmium tetroxide (OsO₄). Lines from the ν₁ totally symmetric stretching fundamental have been assigned. These data together with the infrared assignments of the ν₃ band previously recorded (M. Louviot et al., J. Quant. Spectrosc. Radiat. Transfer, 2012, 113, 119–127) allowed a refinement of the analysis of the ν₁/ν₃ stretching dyad. We found that the ν₁ band has an unusual positive isotopic shift of approximately 0.32 cm^{− 1}/amu, which gives further evidence that the stretching dyad should be perturbed by a complex nearby bending band polyad. This work is part of a global effort to analyze all fundamental bands of OsO₄ to obtain a more precise experimental value of the ground state bond length for this heavy metal‐containing molecule. The result could serve as a benchmark for high‐level quantum chemistry calculations. Copyright © 2012 John Wiley & Sons, Ltd.     

Vibrational properties of Cs4W11O35 and Rb4W11O35 systems: high pressure and polarized Raman spectra

Cs₄ W₁₁O₃₅ (CW) and Rb₄ W₁₁O₃₅ (RW) belong to the class of hexagonal bronzes whose structure originates from the K_xWO₃ superconductor hexatungstate. Charge‐imbalanced tungsten bronzes are dielectric materials with rich polymorphism, ferroelectric properties and second‐harmonic generation. In this work, we report the polarized Raman spectra results for both CW and RW, as well as results of high‐pressure Raman scattering experiments (0.0–11.0 GPa) for the Cs₄ W₁₁O₃₅ system, in which we have observed two structural phase transitions at ∼4 and 7.5 GPa. We discuss these transformations and polarized Raman spectra on the basis of lattice dynamics calculation in the related system KNbW₂O₉. Polarized Raman spectra provide strong indication that the highest wavenumber modes observed in these systems originate from tungsten or oxygen vacancies. The observation of a soft‐like mode indicates that the observed phase transitions exhibit a displacive‐type behavior, thus further indicating that these transformations are likely related to reorientations of the octahedral units. The soft mode nature is discussed as well. PACS: 77.80.Bh; 78.30.Hv; 78.30.‐j. Copyright © 2010 John Wiley & Sons, Ltd.     

Coherent anti‐Stokes Raman scattering in Raman lasers and Raman wavelength converters

In this paper recent research progress on the use of Coherent Anti‐Stokes Raman Scattering (CARS) in Raman lasers and Raman wavelength converters is reviewed. The latest insights in the physical nature and behavior of CARS are addressed, and the recent performance breakthroughs in CARS‐based Raman wavelength conversion are discussed. Based on the new findings regarding the behavior of CARS, a physical explanation for apparent inconsistencies in various experimental observations of Raman wavelength conversion is provided. To conclude it is shown that these recent insights also pave the way to the development of a novel CARS‐based mechanism for reducing the heat dissipation in Raman lasers.     

Vibrational dynamics and structural investigation of 4‐benzoylpyridine

The polarized Raman spectra in different environments along with the IR counterpart of 4‐benzoylpyridine (4‐BOP) were critically analyzed to assign all of its normal modes of vibration. The knowledge of the positions of different excited electronic states (EESs)was obtained from the study of electronic absorption spectra. Measurement of Raman excitation profiles (REPs)of several normal modes was carried out to get insight into structural and symmetry properties of the molecule. All the experimental observations were substantiated and corroborated theoretically by quantum chemical calculations (QCCs). The possibility of exciton splitting of the ¹L_a band has been explored both from theoretical and experimental points of view. Copyright © 2010 John Wiley & Sons, Ltd.     

High‐resolution stimulated Raman spectroscopy and analysis of the ν1 stretching band of GeD4

The high‐resolution stimulated Raman spectrum of the ν₁ band of GeD₄ with natural isotopic abundance germanium has been recorded. It has been analyzed as part of the ν₁/ν₃ stretching dyad. The ν₁ and ν₃ band centers have been deduced for all the isotopologues. Copyright © 2006 John Wiley & Sons, Ltd.     

Two‐dimensional stimulated ultraviolet resonance Raman spectra of tyrosine and tryptophan: a simulation study

We report an ab initio simulation study of the ultrafast broad bandwidth ultraviolet stimulated resonance Raman spectra (SRRS) of l ‐tyrosine, l ‐tryptophan, and trans‐l ‐tryptophan‐l ‐tyrosine (WY) dipeptide. Two‐pulse one‐dimensional SRRS and three‐pulse two‐dimensional SRRS that reveal inter‐residue and intra‐residue vibrational correlations are simulated using electronically resonant or pre‐resonant pulse configurations that select the Raman signal and discriminate against excited state pathways. Multimode effects are incorporated via the cumulant expansion. The two‐dimensional SRRS technique is more sensitive to residue couplings than spontaneous Raman. Copyright © 2013 John Wiley & Sons, Ltd.     

High‐resolution stimulated Raman spectroscopy and analysis of the 2ν10 overtone symmetric motion of C2H4

The high‐resolution stimulated Raman spectrum of the 2ν₁₀ band located at 1664.16 cm⁻¹ of C₂H₄ has been reanalyzed, thanks to the tensorial formalism developed in Dijon for X₂Y₄ asymmetric‐top molecules. A total of 191 lines were assigned and fitted as a single band without including perturbations such as Fermi or Coriolis coupling constants. We obtained a global root mean square deviation of 8.5 × 10⁻³ cm⁻¹. Further investigations are required to include interactions with the ν₂ and ν₇ + ν₁₀ bands. Copyright © 2009 John Wiley & Sons, Ltd.     

Optical phonons in millerite (NiS) from single‐crystal polarized Raman spectroscopy

Although several fundamental physico‐chemical aspects of nickel sulfides have been studied in detail, particularly for millerite (nickel(II) monosulfide), the most common nickel sulfide mineral, no satisfactory investigation of optical vibrational modes has been reported previously. In this paper, we provide a definitive assignment of the optical phonons in millerite, investigated by polarized Raman spectroscopy on an oriented single crystal. The impact of the power of the incident laser beam on the spectra has also been investigated, revealing evidence for degradation in the quality of the spectra at sufficiently high laser power. Copyright © 2008 John Wiley & Sons, Ltd.     

Relaxations and phase transitions phenomena in structurally related tyrosine-derived polyarylates

Abstract

A series of four tyrosine-derived polyarylates with different number of methylene groups in the backbone (y = 2, 4, 6 and 8) were studied by measuring thermally stimulated depolarization currents (TSDC). The low temperature TSDC spectra (80—240K) were analyzed at two different degrees of hydration to assess the effects of small amounts of water in the observed broad and complex β band. Higher temperature TSDC spectra (250 to 350 K) provided the α relaxation peaks associated with the glass transition temperature. The direct signal analysis (DSA) method allowed the decomposition of the complex peaks into elementary processes. The β_i components result from localized motions of molecular segments of variable length molecules whose identities were established in a prior study of polycarbonates. The changes observed in the low and high temperature polarization with the number of backbone methylene groups were interpreted as a combination of flexibility and entanglement phenomena.