MEASUREMENT AND CALCULATION OF SPONTANEOUS EMISSION BRANCHING RATIOS, RELATIVE OSCILLATOR-STRENGTHS, TRANSITION-PROBABILITIES AND LEVEL LIFETIMES FOR ATOMIC URANIUM

We propose a laser induced sensitized fluorescence spectrometry for measuring the spontaneous emission branching ratios o?the transitions from the ten levels 5f36d7s7p-7M7, 5f36d7s7p-7L6, 5f37s27p-5K6, 5f26d27s2 - 5L7, 5f46d7s - 7L6, (17,070cm-1)-5L6, 5f26d27s2-5K6, 6d7s7p-7L5, 5f36d7s7p-7K5 and 5f26d27s2-5I5 to the ground state of atomic uranium (UI) for the first time. Their relative oscillator strengths have been measured by means of hollow cathode discharge (HCD) emission spectrometry. The radiative...

Double injection: high frequency noise and temperature dependence

Noise measurements from 140°K to 350°K ambient temperature and between 10kHz and 22MHz performed on a double injection silicon diode as a function of operating point indicate that the high frequency noise depends linearly on the ambient temperature T and on the differential conductance g measured at the same frequency. The noise is represented quantitatively by〈i^2〉 = α•4kTgΔf. A new interpretation demands Nyquist noise with α ≡ 1 in these devices at high frequencies. This is in accord with an equivalent circuit derived for the double injection process. The effects of diode geometry on the static I-V characteristic as well as on the ac properties are illustrated. Investigation of the temperature dependence of double injection yields measurements of the temperature variation of the common high-level lifetime τ(τ ∝ T^2), the hole conductivity mobility µ_p (µ_p ∝ T^(-2.18)) and the electron conductivity mobility µ_n(µ_n ∝ T^(-1.75)).

掺钕材料激光终态能级寿命测量

介绍了目前测量掺钕材料激光终态能级寿命的三种方法，通过对三种测量方法比较，采用间接法测量激光终态能级寿命相对简单易行。

Dynamics of spin-dependent tunneling through a semiconductor double-barrier structure

The dynamics of spin-dependent tunneling through a nonmagnetic semiconductor double-barrier structure is studied including the k(3) Dresselhaus spin orbit coupling is solved by the time-dependent Schrodinger equation with a developed method for the finite-difference relaxation. The resonant peak and quasibound level lifetime are determined by the in-plane wave vector and the applied electric field. The buildup time and decay lifetime of resonant probability amplitude are different for the spin-down and spin-up electrons due to the Dresselhaus spin-orbit coupling. Further investigation shows that the steady spin-polarization in both the well and collector regions has been obtained in the time domain. (C) 2007 American Institute of Physics.

X-ray spectra induced by Xe-129(q+) impacting the metal surface

Using the slow highly charged ions Xe-129(q+) (q = 25, 26, 27; initial kinetic T-0 <= 4.65 keV/a.u.) to impact Au surface, the Au atomic M alpha characteristic X-ray spectrum is induced. The result shows that as long as the charge state of projectile is high enough, the heavy atomic characteristic X-ray can be effectively excited even though the incident beam is very weak (nA magnitude), and the X-ray yield per ion is in the order of 10(-8) and increases with the kinetic energy and potential energy of projectile. By measuring the Au M alpha-X-ray spectra, Au atomic N-level lifetime is estimated at about 1.33x10(-18) s based on Heisenberg uncertainty relation.

X-ray spectrum emitted by the impact of Xe-129(q+) on Mo surface

We studied the characteristic X-ray spectra produced by the interaction of highly charged ions of X-129(q+) (q =25, 26, 27) with surface of metallic Mo. The experimental result shows that highly charged ions can excite the characteristic X-ray spectra of L-shell of Mo when the beam' s intensity is not more than 120 nA. The X-ray yield of single ion reaches a quantitative level of 10(-8) and increases with the increment of the ion' s kinetic energy and ionic charge (potential energy). By measuring the X-ray spectra of Mo-L alpha(1) the M-level lifetime of Mo atom is estimated by using Heisenberg uncertainty relation.

The effect of hyperfine interaction on the lifetime of the 3s3p P-3(2) level of Mg-like ions

On the basis of previous work, the hyperfine-induced 3s3p P-3(2) -> 3s(2) S-1(0) E1 transition probabilities of Mg-like ions were further calculated using the GRASP2K package based on the multiconfiguration Dirac-Hartree-Fock method. The contribution to the lifetime of the P-3(2) level from the 3s3p P-3(2) -> 3s(2) S-1(0) hyperfine-induced E1, 3s3p P-3(2) -> 3s3p P-3(1) M1, 3s3p P-3(2) -> 3s(2) S-1(0) M2 and 3s3p P-3(2) -> 3s3p P-3(0,1) E2 transition was discussed in detail. It was found that hyperfine interaction has an obvious effect on the lifetime at the beginning of the Mg-like isoelectronic sequence.

"i Went To The Woods Because I Wished To Live Deliberately": How A College-Level Academic Course Can Influence A Lifetime

This study, using the portraiture methodology, provides an analysis of the lifelong significance of an undergraduate program that integrates literature with an outdoor experiential platform. With limited research on long-term effects of an academic outdoor experiential course on one's life, there is space to wonder about the prospect and nature of the long-term significance of an academic course that may offer technical skill, intrapersonal and interpersonal development, and also the delivery of subject matter related to a traditional or mainstream academic area of study. Utilizing an academic skills-oriented lens as well as a character strengths lens, portraits were crafted of four former participants of the University of Michigan's New England Literature Program (NELP) to shed light on the long-term influence of this type of course, crucial participant characteristics that contribute to the program's impact, and specific components of the program that are particularly integral to the course's efficacy. Since 1975, each spring term a small contingent of students and educators has lived in the woods in the New England region as a community of learners, artists and explorers. NELP is an exemplar of a longstanding undergraduate academic English course that integrates the literature of New England writers, exploratory writing and student experiences relating to regional literature and the land. Emergent themes of this course's long-term influence on former participants include increased collaborative skills, increased self-confidence and self-knowledge, a reinforcement of lifelong relationships with the outdoors, and nurtured creativity. For participants to reap benefit from this course, it was important for them to enter with maturity to conduct themselves with openness to new experiences, relationships, and extensive reflection. Findings relating to the integral components of such a program include that of being place-based, oriented towards process, and being an intentional, collaborative community.

Inference for the Component and System Lifetime Distribution of a k-unit Parallel System Based on System Data

In this paper, we consider the inference for the component and system lifetime distribution of a k-unit parallel system with independent components based on system data. The components are assumed to have identical Weibull distribution. We obtain the maximum likelihood estimates of the unknown parameters based on system data. The Fisher information matrix has been derived. We propose -expectation tolerance interval and -content -level tolerance interval for the life distribution of the system. Performance of the estimators and tolerance intervals is investigated via simulation study. A simulated dataset is analyzed for illustration.

Possibility of lifetime measurement in a flowing medium with phase fluorometry

The possibility of lifetime measurement in a flowing medium with phase fluorometry is investigated theoretically. A 3-D time dependent partial differential equation of the number density of atoms (or molecules) in the upper level of the fluorescence transition is solved analytically, taking flow, diffusion, optical excitation, decay, Doppler shift, and thickness of the excitation light sheet into account. An analytical expression of the intensity of the fluorescence signal in the flowing medium is deduced. Conditions are given, in which the principle of lifetime measurement with phase fluorometry in the static sample cell can be used in a flowing medium.

Two-colour laser-induced electron dynamics in two-level quantum system

To attempt to control the quantum state of a physical system with a femtosecond two-colour laser field, a model for the two-level system is analysed as a first step. We investigate the coherent control of the two-colour laser pulses propagating in a two-level medium. Based on calculating the influence of the laser field with various laser parameters on the electron dynamics, it is found the electronic state can be changed up and down by choosing the appropriate laser pulses and the coherent control of the two-colour laser pulses can substantially modify the behaviour of the electronic dynamics: a quicker change of two states can be produced even for small pulse duration. Moreover, the oscillatory structures around the resonant frequency and the propagation features of the laser pulses depend sensitively on the relative phase of the two-colour laser pulses. Finally, the influence of a finite lifetime of the upper level is discussed in brief.

Superluminal optical solitons in a four-level tripod atomic system

With one weak probe field and two strong pumping fields, superluminal optical solitons are formed in a lifetime-broadened four-level tripod atomic medium. With proper parameters, both dark and bright solitons can occur in the highly resonant medium. The corresponding group velocity of the solitons can be superluminal. Meanwhile, the conditions for superluminal solitons occurrence are given.

Optical solitons in a four-level inverted-Y system

With one weak probe field and two strong pumping fields, the possibility of producing superluminal optical solitons is discussed in a lifetime-broadened inverted-Y atomic medium with proper parameters. As the group velocity of the solitons is larger than c, its occurrence can be controlled by modulating the intensities and the detunings of lasers.

Theoretical modelling of the effect of photon lifetime on the output dynamics of Er-doped distributed feedback fibre lasers

By employing a simple model of describing three-level lasers, we have theoretically investigated the effect of photon lifetime on the output dynamics of Er-doped distributed feedback fibre lasers. And based on the theoretical analysis we have proposed a promising method to suppress self-pulsing behaviour in the fibre lasers.

A comparison of methods for assessing the lifetime reliability of a moored FPSO

Current design codes for floating offshore structures are based on measures of short-term reliability. That is, a design storm is selected via an extreme value analysis of the environmental conditions and the reliability of the vessel in that design storm is computed. Although this approach yields valuable information on the vessel motions, it does not produce a statistically rigorous assessment of the lifetime probability of failure. An alternative approach is to perform a long-term reliability analysis in which consideration is taken of all sea states potentially encountered by the vessel during the design life. Although permitted as a design approach in current design codes, the associated computational expense generally prevents its use in practice. A new efficient approach to long-term reliability analysis is presented here, the results of which are compared with a traditional short-term analysis for the surge motion of a representative moored FPSO in head seas. This serves to illustrate the failure probabilities actually embedded within current design code methods, and the way in which design methods might be adapted to achieve a specified target safety level.