1,2-聚丁二烯的固态13C-NMR线宽与自由体积

本工作测定了一系列1,2-聚丁二烯样品在不同温度下的固态¹³C-NMR线宽,研究了线宽对链结构和温度的依赖性;发现在一定的温度范围内,线宽与温度的关系符合WLF方程,这表明高聚物的NMR弛豫不仅取决于分子结构,也与自由体积有关。自由体积理论在NMR弛豫中也是适用的。     

Temperature dependence of Raman linewidth and shift in CuI

The temperature dependence of the optical phonon linewidth and frequency shift in CuI has been measured in the temperature range of 4.2 ～ 300 K. Utilizing phonon dispersion curves obtained from neutron scattering measurements, the linewidths and frequency shifts are calculated in terms of three-phonon interactions proposed by Pine and Tannenwald. The experimental results for the change in linewidth and frequency with temperature are in good agreement with this theory.     

利用钟跃迁谱线测量超稳光学参考腔的零温漂点

在87Sr光晶格钟实验系统中,通过将自由运转的698 nm激光频率锁定在由超低膨胀系数的玻璃材料构成的超稳光学参考腔上,从而获得短期频率稳定性较好的超稳窄线宽激光.超稳光学参考腔的腔长稳定性决定了最终激光频率的稳定度.为了降低腔长对温度的敏感性,使激光频率具有更好的稳定度和更小的频率漂移,利用锶原子光晶格钟的钟跃迁谱线,测量了698 nm超稳窄线宽激光系统中超稳光学参考腔的零温漂点.通过对钟跃迁谱线中心频率随温度的变化曲线进行二阶多项式拟合,得到698 nm超稳窄线宽激光系统的零温漂点为30.63℃.利用锶原子光晶格钟的闭环锁定,测得零温漂点处698 nm超稳窄线宽激光系统的线性频率漂移率为0.15 Hz/s,频率不稳定度为1.6×10^–15@3.744 s.     

Combined effect of light intensity and temperature on the magnetic resonance linewidth in alkali vapor cell with buffer gas

One of the peculiar phenomenons in non-zero magnetic resonance magnetometer is that, with the increase of the temperature, the magnetic resonance linewidth is narrowed at first instead of broadened due to the increasing collision rate. The magnetometer usually operates at the narrowest linewidth temperature to obtain the best sensitivity. Here, we explain this phenomenon quantitatively considering the nonlinear of the optical pumping in the cell and did experiments to verify this explanation. The magnetic resonance linewidth is measured using one amplitude-modulated pump laser and one continuous probe laser. The field is along the direction orthogonal to the plane of pump and probe beams. We change the temperature from 53℃ to 93℃ and the pumping light from 0.1 mW to 2 mW. The experimental results agree well with the theoretical calculations.     

Temperature dependence of thek=0 optical phonons of Bi and Sb

The temperature dependence of the energy and the linewidth of thek=0 optical phonons in Bi and Sb has been measured by Raman Scattering. The decrease in energy with increasing temperature is determined by the thermal expansion of the crystal whereas the increase in linewidth with increasing temperature can be accounted for by a two phonon decay process.     

Feedback cooling of a one-electron oscillator

A one-electron oscillator is cooled from 5.2 K to 850 mK using electronic feedback. Novel quantum jump thermometry reveals a Boltzmann distribution of oscillator energies and directly measures the corresponding temperature. The ratio of electron temperature and damping rate (also directly measured) is observed to be a fluctuation-dissipation invariant, independent of feedback gain, as predicted for noiseless feedback. The sharply reduced linewidth that results from feedback cooling illustrates the likely importance for improved fundamental measurements and symmetry tests.     

Electron spin resonance in nickel near Tc

The temperature dependence of the FMR and EPR linewidth of bulk nickel single crystals was measured from 260 to 410°C at 9.85 GHz. A linewidth falling off rapidly with increasing temperature was found in a region above T_c: 365<T<385°C. An interpretation by the critical behaviour of the spin system is discussed.     

Continuous wave operation of quantum cascade lasers based on vertical transitions at λ=4.6 μm

Continuous wave operation of a quantum cascade laser at λ=4.6 μm is reported above liquid nitrogen temperature. Optical powers of 15 mW at 50 K and 2 mW at 85 K are reported. The single mode spectrum is temperature tunable over 1.8 cm⁻¹. A linewidth of 115 Mhz is measured with a Fabry–Perot on those free running devices. Gain measurements show evidence for ultra low linewidth enhancement factor α<0.1. These devices also operated in pulse mode with 20 mW peak power at 200 K.     

Terahertz absorption spectrum of D2O vapor

The absorption spectrum of D₂O vapor from 0.2 to 2.0 THz (6.7-67 cm⁻¹) which is associated with rotational modes was measured at one atmosphere using terahertz time-domain spectroscopy (THz-TDS). The linewidth and collisional dephasing times were measured for 26 pure rotational transitions in the ground vibrational state (0 0 0). The temperature dependence of the linewidth (Δν) behaves as Δν ∼ T^−3/4 and the linewidth decrease with increasing temperature is attributed to the 1/r⁶ force of interaction between colliding D₂O molecules.     

Correlation effects in the Mössbauer spectra of amorphous metallic magnetic materials

Equations for the mean positions and root mean square (RMS) linewidths of the six-line Mössbauer Zeeman spectrum of ⁵⁷Fe in an amorphous environment have been set out and used to interpret the measured room temperature spectrum for the amorphous metallic ferromagnet Fe₇₆B₂₄. The spectrum exhibits a linewidth asymmetry which is caused by correlations between the various fluctuation variables involved. The major source of this linewidth asymmetry is the correlation between hyperfine field, electric field gradient, and their relative orientation, the dominant physical origin being the angular dependence of the field fluctuations. A smaller, but still significant, additional contribution to linewidth asymmetry arises from correlations between hyperfine field and isomer shift. It is the established beyond question that in neither case can these correlations be represented by a simple linear coupling between the fluctuation variables. The linewidth analysis also provides separate measures of the RMS widths of the hyperfine field, isomer shift, and electric field gradient distributions.     

Temperature dependence of the ESR linewidth in KFeS2

The ESR linewidth in KFeS₂ has been measured in the range 80–340 K. The linewidth is found to decrease steadily as the temperature is increased, without any discontinuity or singularity at the transition temperature T_N=245 K. In the paramagnetic state, the region of enhanced linewidth extends further above T_N than for two-and three-dimensional compounds such as K₂MnF₄ and MnF₂.     

Simulation and measurement of millimeter-wave radiation from Josephson junction array

We report the circuit simulations and experiments of millimeter-wave radiation from a high temperature superconducting(HTS) bicrystal Josephson junction(BJJ) array. To study the effects of junction characteristic parameters on radiation properties, new radiation circuit models are proposed in this paper. The series resistively and capacitively shunted junction(RCSJ) models are packaged into a Josephson junction array(JJA) model in the simulation. The current-voltage characteristics(IVCs) curve and radiation peaks are simulated and analyzed by circuit models, which are also observed from the experiment at liquid nitrogen temperature. The experimental radiation linewidth and power are in good agreement with simulated results. The presented circuit models clearly demonstrate that the inconsistency of the JJA will cause a broad linewidth and a low detected power. The junction radiation properties are also investigated at the optimal situation by circuit simulation. The results further confirm that the consistent JJA characteristic parameters can successfully narrow the radiation linewidth and increase the power of junction radiation.     

Frequency behaviour and linewidth of cw single mode color center lasers

Color center lasers in different alkali halide crystals were found to oscilate in one primary and one or two hole burning modes without using frequency selecting elements. Considering the measured dependence of the linewidth on the disturbing effects as temperature and pump power fluctuations a linewidth of 25 kHz for the free running single mode color center laser is expected.     

ZnCuInS量子点的变温光致发光

测量了红色和深红色发光的ZnCuInS量子点在100~300 K温度范围内的光致发光光谱,研究了ZnCuInS量子点的发光机理,对ZnCuInS量子点的发光峰值能量、线宽和积分强度与温度的关系进行了细致的分析。在ZnCuInS量子点中观察到一种反常的发光峰值能量随着温度升高而增加的现象,同时发现ZnCuInS量子点的发光线宽很宽,约为300 meV,拟合积分强度与温度的关系曲线所得到的激活能为100 meV。这些结果表明,ZnCuInS量子点的发光不可能只来源于一种发光中心,而应该是来源于ZnCuInS量子点内部及表面的多种缺陷相关的多种发光中心组合。     

激光器特性在痕量气体检测中的影响

研究了激光器扫描步长和线宽两种特性对可调谐半导体激光吸收光谱检测系统的影响,理论上推导出激光与气体吸收谱线的作用原理,分析出扫描信号(锯齿波)的台阶间隔和高度影响激光器中心波长的扫描原理.设定了仿真参数,仿真出锯齿波台阶数与最大扫描误差关系曲线,得出扫描信号的一个周期内具有4000个台阶时,半高全宽(FWHM)大于0.01 cm-1,误差小于1‰;仿真出激光器线宽与最大幅值、线宽误差关系曲线,给出线宽误差最大为1%,0.5%时激光器线宽对应的最小FWHM.在温度系数n取0.9,大气展宽系数γair取0.005的条件下,给出温度T,压强P与FWHM关系图,推出了适用的压强与温度范围.为指导选取激光器与气体吸收谱线、提高系统检测限提供了相关理论依据.     

Narrow luminescence linewidth of a silicon quantum dot

Single-dot luminescence spectroscopy was used to study the emission linewidth of individual silicon nanocrystals from low temperatures up to room temperature. The results show a continuous line narrowing towards lower temperatures with a linewidth as sharp as 2 meV at 35 K. This value, clearly below the thermal broadening at this temperature, proves the atomiclike emission from silicon quantum dots subject to quantum confinement. The low temperature measurements further reveal a approximately 6 meV replica, whose origin is discussed. In addition, an approximately 60 meV TO-phonon replica was detected, which is only present in a fraction of the dots.     

纳米尺寸CdS半导体微晶的光致发光线宽宽化研究

测量了各种温度下玻璃中掺杂纳米尺寸CdS半导体微晶的光致发光光谱,研究了其光致发光带的峰值能量和线宽对温度的依赖关系.考虑CdS微晶的LO声子的相互作用,拟合了其带隙发光带的线宽随温度的变化曲线,获得样品的非均匀线宽.CdS微晶的非均匀线宽主要是由于微晶的尺寸分布引起的.     

Linewidth and relative intensity noise measurements of longitudinal modes in ultrahigh-speed mode-locked laser diodes

The longitudinal linewidth and corresponding relative intensity noise (RIN) of 10- and 40-GHz mode-locked laser diodes are measured for the first time to our knowledge. It is shown that the cavity Q value is a dominant parameter of the linewidth. It is also shown that the linewidth of the individual modes is almost constant. This means that the phase noise of each mode is almost the same in the mode-locked condition. The RIN value is larger for modes that are distant from the center longitudinal mode. This mode dependence is a consequence of the mode partition noise.     

纳米尺寸CdS半导体微晶的光致发光线宽宽化研究

测量了各种温度下玻璃中掺杂纳米尺寸ＣｄＳ半导体微晶的光致发光光谱，研究了其光致发光带的峰值能量和线宽对温度的依赖关系．考虑ＣｄＳ微晶的ＬＯ声子的相互作用，拟合了其带隙发光带的线宽随温度的变化曲线，获得样品的非均匀线宽．ＣｄＳ微晶的非均匀线宽主要是由于微晶的尺寸分布引起的．     

Quasi-two-dimensional magnetic properties of an organic ion-radical salt: 3,3′-diethyl-2,2′-selenacyanine-[TCNQ]2

The temperature dependence of the electric conductivity, the spin-susceptibility and the ESR linewidth of an organic ion-radical salt, 3,3′-diethyl-2,2′-selenacyanine-[TCNQ]₂, was measured to elucidate the quasi-two-dimensional magnetic properties of the salt.