Line Shapes Of Transitions Research Articles

The Temperature Dependence of the Quantum Transition Properties of the Quasi-two-dimensional System in Quasi-two-dimensional Semiconductors

We investigated theoretically the temperature dependence of the quantum optical tran- sition of quasi-2-dimensional Landau splitting, in GaN and GaAs. We apply the quantum transport theory (QTR) to a system of electrons confined in a potential. We use the projected Liouville equa- tion method with equilibrium average projection scheme (EAPS). Through the analysis of this work, we found increasing optical quantum transition line shapes (QTLSs) and the quantum tran- sition line widths (QTLWs) in GaN and GaAs with increasing temperature. We also found the temperature dependences of the scattering factor functions: (T) of GaN < (T) of GaAs in the temperature region 50 K < T and (T) of GaAs < (T) of GaN in the temperature T < 50 K and = 394 µm.

A comparative study of the effects of different buffer gases on the line shape of water vapour rovibronic transition

The line shape parameters of water vapour rovibrational transition at 12145.444 cm −1 belonging to the (2 ν 1 + ν 2 + ν 3) overtone band in the presence of three buffer gases He, N 2 and CO 2 are studied by high resolution near infrared (NIR) diode laser spectrometer. The wavelength modulation spectroscopy (WMS) is adopted to probe buffer gas broadened first derivative (1f) signal of water vapour transition. The simulation of the experimental signals based on Voigt profile provides the collisional broadening coefficients and line strength parameters. The comparison is made between the broadening effects on water vapour transition induced by He, N 2 and CO 2.

Trading sensitivity for information: Carr–Purcell–Meiboom–Gill acquisition in solid-state NMR

The Carr-Purcell-Meiboom-Gill (CPMG) experiment has gained popularity in solid-state NMR as a method for enhancing sensitivity for anisotropically broadened spectra of both spin 1/2 and half integer quadrupolar nuclei. Most commonly, the train of CPMG echoes is Fourier transformed directly, which causes the NMR powder pattern to break up into a series of sidebands, sometimes called "spikelets." Larger sensitivity enhancements are observed as the delay between the pi pulses is shortened. As the duration between the pi pulses is shortened, however, the echoes become truncated and information about the nuclear spin interactions is lost. We explored the relationship between enhanced sensitivity and loss of information as a function of the product Omega 2tau, where Omega is the span of the anisotropic lineshape and 2tau is the pi pulse spacing. For a lineshape dominated by the nuclear shielding anisotropy, we found that the minimum uncertainty in the tensor values is obtained using Omega 2tau values in the range Omega 2tau approximately 12(-1)(+6) and Omega 2tau approximately 9(-3)(+3) for eta(s)=0 and eta(s)=1, respectively. For an anisotropic second-order quadrupolar central transition lineshape under magic-angle spinning (MAS), the optimum range of Omega 2tau approximately 9(-2)(+3) was found. Additionally, we show how the Two-dimensional One Pulse (TOP) like processing approach can be used to eliminate the cumbersome sideband pattern lineshape and recover a more familiar lineshape that is easily analyzed with conventional lineshape simulation algorithms.

A velocity map imaging study of gold-rare gas complexes: Au–Ar, Au–Kr, and Au–Xe

The ultraviolet photodissociation dynamics of the gold-rare gas atom van der Waals complexes (Au-RG, RG = Ar, Kr, and Xe) have been studied by velocity map imaging. Photofragmentation of Au-Ar and Au-Kr at several wavelengths permits extrapolation to zero of the total kinetic energy release (TKER) spectra as monitored in the Au((2)P(3/2)(o)[5d(10)6p]) fragment channel, facilitating the determination of ground state dissociation energies of D(0)(")(Au-Ar) = 149+/-13 cm(-1) and D(0)(")(Au-Kr) = 240+/-19 cm(-1), respectively. In the same spectral region, transitions to vibrational levels of an Omega(') = 1/2 state of the Au-Xe complex result in predissociation to the lower Au((2)P(1/2)(o)[5d(10)6p])+Xe((1)S(0)[5p(6)]) fragment channel for which TKER extrapolation yields a value of D(0)(")(Au-Xe) = 636+/-27 cm(-1). Asymmetric line shapes for transitions to the v(') = 14 level of this state indicate coupling to the Au((2)P(3/2)(o)[5d(10)6p])+Xe((1)S(0)[5p(6)]) continuum, which allows us to refine this value to D(0)(")(Au-Xe) = 607+/-5 cm(-1). The dissociation dynamics of this vibrational level have been studied at the level of individual isotopologues by fitting the observed excitation spectra to Fano profiles. These fits reveal a remarkable variation in the predissociation dynamics for different Au-Xe isotopologues. For Au-Ar and Au-Xe, the determined ground state dissociation energies are in good agreement with recent theoretical calculations; the agreement of the Au-Kr value with theory is less satisfactory.

Ne II FINE-STRUCTURE LINE EMISSION FROM THE OUTFLOWS OF YOUNG STELLAR OBJECTS

The flux and line shape of the fine-structure transitions of \NeII\ and \NeIII\ at 12.8 and 15.55\,$\mu$m and of the forbidden transitions of \OI\ $\lambda6300$ are calculated for young stellar objects with a range of mass-loss rates and X-ray luminosities using the X-wind model of jets and the associated wide-angle winds. For moderate and high accretion rates, the calculated \NeII\ line luminosity is comparable to or much larger than produced in X-ray irradiated disk models. All of the line luminosities correlate well with the main parameter in the X-wind model, the mass-loss rate, and also with the assumed X-ray luminosity --- and with one another. The line shapes of an approaching jet are broad and have strong blue-shifted peaks near the effective terminal velocity of the jet. They serve as a characteristic and testable aspect of jet production of the neon fine-structure lines and the \OI\ forbidden transitions.

CaTiO 3:Eu 3+ obtained by microwave assisted hydrothermal method: A photoluminescent approach

Europium doped calcium titanate (CT:Eu 3+) powders containing 0.5%, 1.0% and 2.0% mol of Eu 3+ were synthesized by hydrothermal microwave method (HTMW) at 140 °C for 10 min resulting in the samples CT:Eu 3+ (0.5%) CT:Eu 3+ (1.0%) and CT:Eu 3+ (2.0%). Eu 3+ ion was introduced into the perovskite lattice aiming to study the synthesis, photoluminescence emissions and morphological properties of these powders. X-ray diffraction patterns present a single phase indexed as Pbnm space group in a typical orthorhombic CaTiO 3 (CT) structure. FT-Raman spectra of CT indicated a great arrangement in a short range, while UV–vis measurements did not show any substantial changes in the optical absorbance behavior of CT:Eu 3+ samples. The existence of two small absorbance bands at 394 and 466 nm suggests the presence of Eu 3+ in the CT lattice, confirmed by excitation and photoluminescence emission spectra. The emission line shape transitions from 5D 0 to 7F J ( J = 0, 1–4) levels of the Eu 3+ was noticed at, respectively 579, 589, 613, 654 and 695 nm, and the most intense one at 613 nm is ascribed to the hypersensitive 5D 0 → 7F 2 transition. Among the samples, the most intense photoluminescence results were observed for the CT:Eu 3+ (1.0%).

Excited spectator electron effects on spectral line shapes

Excited spectator electron effects on Stark broadened spectral line shapes of transitions involving tightly bound electrons are investigated. It is shown that the interference terms in the electron impact broadening are essential to describe the overlapping lines generated by these configurations (e.g.; dielectronic satellite lines). The main impact is narrower spectral features and reduced far wing intensities compared to calculations neglecting the interference terms.

THE THERMAL OPTICAL QUANTUM TRANSITION PROPERTIES OF PIEZOELECTRIC MATERIALS UNDER OSCILLATING EXTERNAL FIELD

ABSTRACT We consider two systems—the one system is subject to circularly polarized oscillatory external fields and the other system is subject to linearly polarized oscillatory external field. The main purpose of this work is that comparisons of the optical quantum transition line shapes (QTLS) which show the absorption power and the quantum transition line widths (QTLW) in both directional polarized oscillatory external field. Our results indicate that the QTLS of circularly polarized oscillatory external field is larger than the QTLS of linearly polarized oscillatory external field, while the opposite result is obtained for the QTLW. In both directional polarized oscillatory external field, we analyze the temperature dependence of the QTLS and the QTLW in various cases. In order to analyze the quantum transition, we compare the temperature dependence of the QTLW and QTLS of two transition process, the intra Landau level transition process and the inter Landau level transition process. We study the thermal properties of electron-piezoelectric phonon interacting system in the confinement of electrons by square well confinement potential. We use the projected Liouville equation method with Equilibrium Average ProjectionScheme (EAPS).

THE MAGNETIC FIELD DEPENDENCE PROPERTIES OF ELECTRON-PIEZOELECTRIC PHONON INTERACTING MATERIALS IN SQUARE WELL CONFINEMENT POTENTIAL

ABSTRACT We consider the system is subject to the linearly polarized oscillatory external field. We study the optical quantum transition line shapes (QTLS) which show the absorption power and the quantum transition line widths (QTLW) of electron-piezoelectric phonon interacting system. We analyze the magnetic field dependence of the QTLS and the QTLW in various cases. In order to analyze the quantum transition, we compare the magnetic field dependence of the QTLW and QTLS of two transition process, the intra-Landau level transition process and the inter-Landau level transition process.

Pr3+ doped LaTiNbO6 as a single phosphor for white LEDs

A structurally disordered host crystal, LaTiNbO6, has been doped with the Pr3+ ions emitting at two wavelength regions that could be mixed to give out white light. In agreement with the structural design, the samples showed inhomogeneously broadened transition lineshape arising from the disorder, which is not only efficient for the absorption of blue LED sources, but also insensitive to temperature variations. Aeschynite-structured LaTiNbO6 allowed doping of up to 100% Pr3+ without phase segregation. The samples gave out two clusters of dominant emissions peaked at 490 nm (3P0 → 3H4) and 609 nm (3P0 → 3H6), respectively, whose relative intensities could be tuned by the doping level to give a desired chromaticity.

Line shape of the μH(3p - 1s) transition

The line shape of the (3p − 1s) X-ray transition in muonic hydrogen was measured for the first time with a high-resolution crystal spectrometer. The assumption of a statistical population of the hyperfine levels was directly confirmed by experiment, and a measured value for the hyperfine splitting is reported. An X-ray line broadening due to Doppler effect could be clearly identified and attributed to different Coulomb de-excitation transitions which precede the measured radiative transition. The results allow a decisive test of advanced cascade model calculations and establish an alternative and “model free” method to extract the strong-interaction parameters from pionic hydrogen data.

All-optical cw quadruple resonance excitation: A coherently driven five-level molecular system

We report here a continuous-wave, high-resolution, and all-optical quadruple resonance laser excitation experiment. To demonstrate this excitation technique, we have used an inhomogeneously broadened molecular sample (Na-2). We emphasize the enhanced ability afforded by the technique to reach new ranges of internuclear separation as well as access to a large range of molecular electronic states. Using the Autler-Townes split line shape of a rovibronic transition and the E field amplitude of the corresponding coupling laser, we have measured with high precision the absolute value of the molecular electronic transition dipole moment matrix elements, with more flexibility than the double and the triple resonance based excitation schemes used previously. This technique may also be used in a stimulated Raman adiabatic passage configuration for effective transfer of ultracold molecules, formed at long internuclear distance, to the lowest vibrational level of the ground electronic state. (Less)

The magnetic field dependence of the deformation potential materials in the square well confinement potential

Abstract We study the optical Quantum Transition Line Shapes (QTLS) which show the absorption power and the Quantum Transition Line Widths (QTLW) of electron-deformation potential phonon interacting systems. In order to analyze the quantum transition, we compare the magnetic field dependencies of the QTLWand the QTLS on two transition processes, namely the intra-Landau level transition process and the inter-Landau level transition process. We apply the Quantum Transport theory (QTR) to the system in the confinement of electrons by square well confinement potential. We use the projected Liouville equation method with Equilibrium Average Projection Scheme (EAPS).

Spatial and temporal probing of a laser-induced plasma plume by cavity ringdown spectroscopy

The laser-induced plasma plume of a Ti target in vacuum is probed by the technique of cavity ringdown spectroscopy. A model is developed to perform a forward convolution of atomic absorption line profile measurements. The model accounts for laser-induced plasma characteristics such as anisotropy of the plume and velocity distributions of the ablated particles as well as of the cavity ringdown features such as geometry and time selectivity. The absorption lineshapes of atomic transitions are calculated and discussed for given sets of parameters. Calculated line profiles are fitted to experimental line profiles obtained from nanosecond-laser ablation of the target and provide data about the plume dynamics.

Magnetic Properties of Optical Quantum Transition Line Shapes and Line Widths of Electron–Piezoelectric Potential Phonon Interacting Materials under Circularly Oscillating Fields

We study optical quantum transition line shapes (QTLSs) and optical quantum transition line widths (QTLWs) in relation to magnetic-field dependence properties of the electron–piezoelectric potential phonon interaction system. We consider two systems – one is subject to right circularly oscillating external fields and the other is subject to left circularly oscillatory external fields. The main purpose of this work is to compare QTLSs, which indicate absorption power, in the two oscillating external fields. Our results indicate that the QTLSs of right circularly oscillating external fields is larger than the QTLSs of left circularly oscillating external fields, while the opposite result is obtained for the QTLWs.

Radiative Transition Line Shape in Warm and Dense Argon Plasma: a Two-Centre Model Study

A two-centre model is employed to study the electronic structure of argon plasma at a density of 1022 cm−3 and a temperature of 5eV. The model takes into account the influence of the nearest neighbour on the electronic structure of the radiator and gives a proper description of the transient molecular behaviour in dense plasmas where the mean interatomic distance can be the order of the orbital spatial extent. The orbital energies of quasi-molecular Ar2 against the interatomic distance are calculated in the framework of density functional theory. It is shown that the orbital energies are not monotonic functions of the distance because of two competitive effects: the repulsive potential between electrons and the attractive potential between electrons and nuclei. The characteristics of this two-centre system can be categorized by three regimes depending on the ratio between the electron wavelength and the interatomic distance: atomic regime, screened atomic regime, and quasi-molecular regime. This classification agrees qualitatively with the conclusion of full quantum-mechanical approach [Yonger S Met al 1988 Phys. Rev. Lett. 61 962].

THE TEMPERATURE PROPERTIES OF THIN FILM PIEZOELECTRIC MATERIALS

ABSTRACT Based on quantum transport theory, we analysis the temperature dependence of optical quantum transition line shapes (QTLS) of GaAs and CdS in some temperatures, through the numerical analysis of theoretical result. We study the thermal properties of electron-piezoelectric phonon interacting system in the confinement of electrons by square well confinement potential. In order to analysis the quantum transition process, we compare the temperature dependence of the QTLW and the QTLS of two transition process, which are the phonon emission transition process and the phonon absorption transition process. We use the theory of the projected Liouville equation method with Equilibrium Average Projection Scheme (EAPS).

Nonresonant effects and hydrogen transition line shape in cosmological recombination problems

Data on the fluctuations in cosmic microwave background (CMB) radiation, whose accuracy is expected to increase in the immediate future, allow the cosmological recombination of atomic hydrogen and its interaction with the CMB radiation to be studied. Nonresonant effects play an important role in these recombination processes. We consider the quantum-mechanical foundations of the nonresonant processes and present our calculations for the differential two-photon decay rates of the 3s and 3d levels in the hydrogen atom.

Femtosecond Spectral Hole Burning Spectroscopy as a Probe of Exciton Dynamics in Quantum Dots

We present measurements of the dynamics of photoexcited excitons inan ensemble of InAs/GaAs self-assembled quantum dots using a femtosec-ond spectral hole burning technique. We use this technique to examine theexciton spin relaxation and the line shape of optical transitions in the dots.PACS numbers: 73.21.La, 78.47.{p, 78.67.Hc

Generation of Interstellar Class II 7 2 –8 1 A + and 7 2 –8 1 A - Methanol Masers

New methanol maser lines at 72?63A?(86.6 GHz) and 72?63A+(86.9 GHz) together with two candidate methanol maser lines at 72?81A?(80.99 GHz) and 72?81A+(111.29 GHz) have been detected in W3(OH). We use a pumping mechanism, i.e., methanol masers without population inversion, to explain the formation of weak methanol masers of 72?81A+ and 72?81A?. We explain well why the line-shape of the transition 72?81A+ is not typical. A similar argument can be applied to the ?-type level system 72A?, 63A? and 81A?, as well as to the 72?81A? 80.99 GHz masers.