双光子J-C模型中原子和场的熵特性

研究了双光子J-C模型中原子和场线性熵的演化规律，讨论了原子初态对原子和光场线性熵的影响，结果表明，当原子初始处于纯态时，在原子布居回复周期Tr处，原子（场）的线性熵趋近于零；当原子初始处于混态时，在原子布居回复周期Tr处，原子线性熵较大，而场的线性熵接近于零，在t=π／4g和t=3π／4g处，原子的线性熵有极小值，而场的线性熵较大。     

灰体场中原子和光场的熵交换研究

研究了二能级原子与灰体场相互作用过程中原子和光场线性熵的交换规律,讨论了失谐量以及腔场光子数分布对原子和光场线性熵交换的影响。结果表明,原子和光场线性熵的振动周期由失谐量决定,熵交换量的振幅与入射光强度、腔体温度及吸收系数有关。     

灰体场中原子和光场的熵交换研究

研究了二能级原子与灰体场相互作用过程中原子和光场线性熵的交换规律,讨论了失谐量以及腔场光子数分布对原子和光场线性熵交换的影响。结果表明,原子和光场线性熵的振动周期由失谐量决定,熵交换量的振幅与入射光强度、腔体温度及吸收系数有关。     

原子与压缩真空场线性熵的演化特性

研究了二能级原子与压缩真空场相互作用系统中原子和场线性熵的演化规律。在弱压缩真空场作用下,原子和场线性熵的振荡频率依赖于原子的初态。当原子初始处于纯态,原子和场线性熵的演化完全相同;当原子处于混态时,原子和压缩真空场线性熵的变化有着负关联。在强压缩真空场作用下,原子线性熵的演化与原子的初始状态无关。     

含时非线性J-C模型中光场的振幅平方压缩效应

讨论了当初始光场处于相干态,原子处于激发态时,非线性J-C模型中光场的振幅平方压缩效应。结果发现,平均光子数n-和脉冲宽度L对压缩深度和压缩时间产生了很大的影响。当脉冲宽度L一定时,压缩深度随着光场平均光子数-n的增加而增大;当平均光子数n-一定时,随着脉冲宽度L的增加,压缩次数和压缩时间区域逐渐增加。     

与时间有关的非线性J-C模型中原子动力学行为研究

研究了与时间有关的非线性J-C模型中的原子动力学行为,讨论了原子与光场以时间脉冲的形式耦合时其脉冲宽度和腔场的平均光子数对原子动力学行为的影响。结果发现,当腔场的平均光子数一定时,随着脉冲宽度的增大原子崩塌与回复次数增多,崩塌时间和回复周期变小;而当脉冲宽度一定时,随着腔场的平均光子数的增大原子的崩塌时间和回复周期逐渐减小。     

与时间有关的非线性J-C模型中原子动力学行为研究

研究了与时间有关的非线性 J-C 模型中的原子动力学行为,讨论了原子与光场以时间脉冲的形式耦合时其脉冲宽度和腔场的平均光子数对原子动力学行为的影响。结果发现,当腔场的平均光子数一定时,随着脉冲宽度的增大原子崩塌与回复次数增多,崩塌时间和回复周期变小;而当脉冲宽度一定时,随着腔场的平均光子数的增大原子的崩塌时间和回复周期逐渐减小。     

灰体腔中场的线性熵研究

研究了与灰体辐射场相互作用的J-C模型中场的线性熵的演化规律,讨论了腔体吸收系数、入射场的光子数分布、热场的平均光子数对场的线性熵的影响.结果表明,灰体辐射场中光场的线性熵依赖于腔体吸收系数、入射场的光子数分布和热场的平均光子数.     

孤立原子和双模腔内原子之间的纠缠突然死亡研究

通过计算并发度和线性熵研究了初始处于纠缠态的两个两能级原子与双模场相互作用系统的纠缠动力学特性,讨论了原子初始纠缠度和腔场初始纠缠度对并发度的影响。结果表明,两原子之间的纠缠出现纠缠突然死亡(ESD)现象,纠缠死亡持续的时间长度和原子初始的纠缠度无关,然而依赖于腔场初始纠缠度;在整个时间演化过程中,两原子和腔场之间一直保持着纠缠状态。     

利用耦合双原子与单模光场相互作用系统实现控制非门

提出一种利用耦合双原子与单模光场相互作用系统实现控制非门的方案.结果表明:腔场初始时刻制备于相干态,双原子处于特定的初态,在大失谐相互作用情况下,通过控制腔场与耦合双原子的相互作用时间,就可以实现控制非门.     

相位损耗对Jaynes-Cummings模型的动力学性质的影响

运用密度算符间距研究了一位于相位损耗腔中大失谐二能级原子与相干光场相互作用系统中原子、光场及系统各态随时间的演化规律,讨论了原子初态、光场的平均光子数和相位损耗对Jaynes-Cummings模型动力学行为的影响.     

Rotationally resolved infrared spectrum of the charge transfer complex [Ar-N2]+

Difficulties in preparing cluster ions for spectroscopic studies have limited our understanding of intermolecular forces in charged complexes that are typical of many reactive intermediates. Here, the infrared spectrum of the charge transfer complex [Ar-N2]+, recorded in a supersonic planar plasma with a tunable diode laser spectrometer, is presented. More than 70 adjacent rovibrational transitions were measured near 2272 wave numbers and assigned to the molecular nitrogen stretching fundamental in the 2Sigma+ ground state of [Ar-N2]+. The accurate structural parameters that were determined confirm a linear structure and show that the major part of the charge is located at the argon atom. The latter result is surprising and implies a charge switch of the cationic center upon complexation.     

Correlations between ground and excited state spectra of a quantum Dot

The ground and excited state spectra of a semiconductor quantum dot with successive electron occupancy were studied with linear and nonlinear magnetoconductance measurements. A direct correlation was observed between the mth excited state of the N-electron system and the ground state of the (N + m)-electron system for m up to 4. The results are consistent with a single-particle picture in which a fixed spectrum of energy levels is successively filled, except for a notable absence of spin degeneracy. Further departures from the single-particle picture due to electron-electron interaction were also observed. Magnetoconductance fluctuations of ground states show anticrossings where wave function characteristics are exchanged between adjacent levels.     

利用耦合双原子与单模光场相互作用系统实现控制非门

提出一种利用耦合双原子与单模光场相互作用系统实现控制非门的方案.结果表明：腔场初始时刻制备于相干态,双原子处于特定的初态.在大失谐相互作用情况下,通过控制腔场与耦合双原子的相互作用时间,就可以实现控制非门.     

Optical pumping and vibrational cooling of molecules

The methods producing cold molecules from cold atoms tend to leave molecular ensembles with substantial residual internal energy. For instance, cesium molecules initially formed via photoassociation of cold cesium atoms are in several vibrational levels nu of the electronic ground state. We applied a broadband femtosecond laser that redistributes the vibrational population in the ground state via a few electronic excitation/spontaneous emission cycles. The laser pulses are shaped to remove the excitation frequency band of the nu = 0 level, preventing re-excitation from that state. We observed a fast and efficient accumulation ( approximately 70% of the initially detected molecules) in the lowest vibrational level, nu = 0, of the singlet electronic state. The validity of this incoherent depopulation pumping method is very general and opens exciting prospects for laser cooling and manipulation of molecules.     

Entropy Estimates for Some Silicates at 298{degrees}K from Molar Volumes

Third law entropies for silicates of Be, Mg, Ca, Zn, Na, and K containing the same anion group, for example, SiO(4) or SiO(3) or AlSi(3)O(8), are found to be linearly related to their molar volumes. The relationship between the molar volume and the entropy of silicates of Fe and Mn, atoms with unfilled d electron subshells, is different from that of other silicates. The linear correlations yield a useful method of estimating the entropies of ortho-, meta-, and framework silicates (feldspars and feld-spathoids). The estimated entropies of pyrope and almandine at 298 degrees K are 47.47 and 68.13 gibbs per mole, respectively.     

低维周期量子点中极化子压缩效应

研究了低维周期对称量子点中极化子的压缩效应。通过引入单模压缩态,改进了Lee-Low-Pines和Huybrechts(LLP-H)方法,并计算了压缩态下极化子的能量。该计算方法不仅适用于所有的耦合常数范围,而且还可以考虑LLP-H方法中忽略了的哈密顿量中声子算符的线形项以及双线形项。将该计算方法所得到的低维周期对称量子点中极化子基态下极化子结合能和势能与LLP-H方法的计算结果相比较,计算结果更加精确。     

A Bose-Einstein condensate of metastable atoms

We report the realization of a Bose-Einstein condensate of metastable atoms (helium in the lowest triplet state). The excitation energy of each atom with respect to the ground state is 20 electron volts, but inelastic processes that would destroy the sample are suppressed strongly enough in a spin-polarized sample to allow condensation. Our detection scheme takes advantage of the metastability to achieve detection of individual atoms as well as of the decay products of inelastic processes. This detection opens the way toward new studies in mesoscopic quantum statistical physics, as well as in atomic quantum optics.