Uniaxial stress and polarisation studies of F2 centre luminescence in MgO

Uniaxial stress and polarised luminescence measurements of additively coloured MgO show that the 375 nm luminescence band is associated with pairs of F centres in nearest neighbour sites along 〈110〉 crystal directions (i.e. F₂ centres).     

Metal nanoparticle-doped coloured films on glass and polycarbonate substrates

In a program on the development of metal (e.g. Au, Ag, Cu and their alloy) nanoparticles in sol-gel derived films, attempts were made to synthesize different coloured coatings on glasses and plastics. The absorption position of surface plasmon resonance (SPR) band arising from the embedded metal nanoparticles was tailored by controlling the refractive index of the matrix for the development of different colours. Thus different coloured (pink to blue) coatings on ordinary sheet glasses were prepared by generating Au nanoparticles in mixed SiO₂-TiO₂ matrices having refractive index values ranging from about 1.41 to 1.93. In another development,in situ generation of Ag nanoparticles in the inorganic-organic hybrid host leads to the formation of different abrasion resistant coloured coatings (yellow to pink) on polycarbonate substrates after curing. As expected, the SPR peak of Ag or Au is gradually red-shifted due to the increase of refractive index of the coating matrices causing a systematic change of colour     

Radiation induced structure defect in multicomponent phosphate glasses doped with manganese

Absorption of multicomponent alumino-phosphate glasses containing manganese up to 20 mol%, irradiated with X or-rays or additively colorated and annealed at 400–450 °C, has bsen measured. After irradiation an absorption band at about 240 nm (D band) appeared. Its intensity increased with increasing radiation dose. It did not occur in additively coloured glasses. On the other hand, the D band arose, as rule, in as-prepared glasses under oxidation conditions. It is, therefore, assumed that the nature of the D band would be the same in both cases. The model of the defect and the mechanism of the formation of this defect is proposed and the role of the Mn concentration is demonstrated.     

Oxide films of copper prepared by the oxidation of copper sulphide films

Copper sulphide films prepared by reactive evaporation, when heated in air at 500 K, oxidized to Cu₂O after a series of intermediate chemical transitions. Golden yellow coloured Cu₂O films showed a large absorption before the fundamental absorption edge. The optical band gap was found to be (2.29±0.02)eV. When these Cu₂O films were further heated they got converted to CuO and the optical band gap was found to be (2.17±0.02)eV.     

Colour centres in powdered KI

Fine powder of KI was coloured in an electrodeless discharge. Due to quick bleaching of the F centres produced in this method, it was possible to prepare the samples that were almost free from the F centres. High concentration of the electron deficient centres could be produced, which were studied by measuring the diffused reflectance. A band at 354 nm is shown to be composed of two overlapping bands. Further, growth of a band appearing at 265 nm is studied. Bleaching characteristics of the samples are studied and it is shown that, similar to F centre bleaching, bleaching of these samples also proceeds in at least two steps. The difference between two components of the bleaching curves is quite marked. Further it is showed that the components are related to the presence of different absorption bands and appear at different stages of colouration.     

彩色发光涂料的光学测量

彩色发光涂料是一种高光效、长余辉的光致发光材料。当对其进行光学测量时,为避免因激发光被探测器接收而对测量结果产生的影响,提出在实验中如何设定特殊的装置,从而保障对发光涂料的光学特性进行有效的测量。根据光度学理论中有关照度和发光亮度的关系,通过实验对三种不同的彩色发光涂料在同样光照条件下的亮度测量,同一种发光涂料在不同颜色光照下的发光亮度比较,以及在彩色发光涂料的亮度衰减情况给出了测量的结果。     

The coloured quantum plane

We study the quantum plane associated to the coloured quantum group GL_q^λ,μ(2) and solve the problem of constructing the corresponding differential geometric structure. This is achieved within the R-matrix framework generalising the Wess–Zumino formalism and leads to the concept of coloured quantum space. Both the coloured Manin plane as well as the bicovariant differential calculus exhibit the colour exchange symmetry. The coloured h-plane corresponding to the coloured Jordanian quantum group GL_h^λ,μ(2) is also obtained by contraction of the coloured q-plane.     

Structural, optical and electrochromic properties of nickel oxide thin films grown from electrodeposited nickel sulphide

Nickel oxide thin films were grown onto FTO-coated glass substrates by a two-step process: electrodeposition of nickel sulphide and their thermal oxidation at 425, 475 and 525 °C. The influence of thermal oxidation temperature on structural, optical, morphological and electrochromic properties was studied. The structural properties undoubtedly revealed NiO formation. The electrochromic properties were studied by means of cyclic voltammetry. The films exhibited anodic electrochromism, changing from a transparent state to a coloured state at +0.75 V versus SCE, i.e. by simultaneous ion and electron ejection. The transmittance in the coloured and bleached states was recorded to access electrochromic quality of the films. Colouration efficiency and electrochromic reversibility were found to be maximum (21 mC/cm² and 89%, respectively) for the films oxidized at 425 °C. The optical band gap energy of nickel oxide slightly varies with increase in annealing temperature.     

Duality for Coloured Quantum Groups

Duality between the coloured quantum group and the coloured quantum algebra corresponding to GL(2) is established. The coloured L ^± functionals are constructed and the dual algebra is derived explicitly. These functionals are then employed to give a coloured generalisation of the differential calculus on quantum GL(2) within the framework of the R-matrix approach.     

Photoluminescence of F2+2 centres in additively coloured magnesium oxide

The principle luminescence bands excited in additively coloured MgO by radiation in the wavelength range 170–400 nm are observed at wavelengths of 520, 475, 441 and 375 nm. Polarised luminescence and uniaxial stress measurements on the 441 nm band, the radiative lifetime of 25 msec at 1.6 K and temperature dependence of luminescence intensities of the 375, 441 and 375 nm bands are consistent with the 441 nm band being due to ³B_1u → ¹A_g transitions of the F²⁺₂ centre.     

Direct study of the lifetime and acceleration of a coloured nucleon

We propose a method of studying directly the confinement part of the force due to the coloured field, and the time that a coloured hadron remains coloured. Applying the method topp→pX data we find that the mean time for colour neutralization of a coloured nucleon is 1.2±0.1 fm/c or (3.9±0.3)×10^?24 s.     

Mobile interstitial model and mobile electron model of mechano-induced luminescence in coloured alkali halide crystals

A theoretical study is made on the mobile interstitial and mobile electron models of mechano-induced luminescence in coloured alkali halide crystals. Equations derived indicate that the mechanoluminescence intensity should depend on several factors like strain rate, applied stress, temperature, density of F-centres and volume of crystal. The equations also involve the efficiency and decay time of mechanoluminescence. Results of mobile interstitial and mobile electron models are compared with the experimental observations, which indicated that the latter is more suitable as compared to the former. From the temperature dependence of ML, the energy gaps between the dislocation band and ground state of F-centre is calculated which are 0.08, 0.072 and 0.09 eV for KCl, KBr and NaCl crystals, respectively. The theory predicts that the decay of ML intensity is related to the process of stress relaxation in crystals.     

Formation and instability of spiral wave induced by Gaussian coloured noise

In this paper, we studied the effect of Gaussian coloured noise on the formation and instability of spiral waves described by one class of modified FitzHugh--Nagumo equation. It was found that Gaussian coloured noise plays a constructive role in the formation, transition and instability of spiral wave. Too weak or too strong noise may act against the formation of spiral waves. At a certain noise level, spiral wave is maintained in a medium, in which spiral wave cannot be observed in the absence of the noise. It is difficult to make a stable spiral wave into unstable state by Gaussian coloured noise, unless the noise level is very high. The parameter regions of Gaussian coloured noise for spiral forming and spiral instability were given and discussed with numerical simulations.     

天然有色水晶的压电振盪性能

本文的目的在于研究天然有色水晶在当作压电共振器用时它的压电振荡性能,并与无色水晶在这方面的性能上作一比较,以推断有色水晶是否可以应用到实际的控制电路振荡的工作中去。我们的工作分四方面进行:(一)有色水晶压电振荡的频率常数,(二)有色水晶压电振荡的稳定性,(三)有色水晶压电振荡的选择性及活动性,(四)有色水晶压电振荡的频率——温度系数。并且把有色水晶在用热处理方法去色后的这四方面实验结果与去色前的作一比较。实验的结果证明有色水晶是可以被激发压电振荡的,和无色水晶一样可以作控制电路振荡之用。有色水晶的Y-截法的频率常数比无色水晶的约低2％。至于两种水晶的其余两种X-截法及AT-截法的频率常数基本上无差别。热处理能使两种水晶的三种截法的压电振荡频率有增高的倾向,这效应在有色水晶中更为显著。同样,热处理对于两种水晶三种截法的压电振荡的选择性及活动性,在统计数字上看来是有益处的。最后,就以上测量的结果,推算了并讨论了有色水晶和无色水晶的若干劲度系数异同之点。     

Transitions in a genotype selection model driven by coloured noises

This paper investigates a genotype selection model subjected to both a multiplicative coloured noise and an additive coloured noise with different correlation time τ1 and τ2 by means of the numerical technique. By directly simulating the Langevin Equation, the following results are obtained. （1） The multiplicative coloured noise dominates, however, the effect of the additive coloured noise is not neglected in the practical gene selection process. The selection rate μ decides that the selection is propitious to gene A haploid or gene B haploid. （2） The additive coloured noise intensity and the correlation time τ2 play opposite roles. It is noted that α and τ2 can not separate the single peak, while can make the peak disappear and ~-2 can make the peak be sharp. （3） The multiplicative coloured noise intensity D and the correlation time τ1 can induce phase transition, at the same time they play opposite roles and the reentrance phenomenon appears. In this case, it is easy to select one type haploid from the group with increasing D and decreasing τ1.     

Upper bound for the time derivative of entropy for a dynamical system driven by coloured cross-correlated white noises

It is shown how the cross-correlation time and strength of coloured cross-correlated white noises can set an upper bound for the time derivative of entropy in a nonequilibrium system. The value of upper bound can be calculated directly based on the Schwartz inequality principle and the Fokker--Planck equation of the dynamical system driven by coloured cross-correlated white noises. The present calculations can be used to interpret the interplay of the dissipative constant and cross-correlation time and strength of coloured cross-correlated white noises on the upper bound.     

Jordanian Uh,sgl(2) and its Coloured Realization

A two-parametric nonstandard (Jordanian) deformation of the Lie algebra gl(2) is constructed and then, exploited to obtain a new, triangular R-matrix solution of the coloured Yang–Baxter equation. The corresponding coloured quantum group is presented explicitly.     

Additive Temporal Coloured Noise Induced Eckhaus Instability in Complex Ginzburg-Landau Equation System

The effect of additive coloured noises, which are correlated in time, on one-dimensional travelling waves in the complex Ginzburg-Landau equation is studied by numerical simulations. We found that a small coloured noise with temporal correlation could considerably influence the stability of one-dimensional wave trains. There exists an optimal temporal correlation of noise where travelling waves are the most vulnerable. To elucidate the phenomena, we statistically calculated the convective velocities Vg of the wave packets, and found that the coloured noise with an appropriate temporal correlation can decrease Vg, making the system convectively more unstable.     

Coloured noise controlled dynamics of nonlinear polaritons in semiconductor microcavity

The coloured noise induced escape rate from the lower energy stable state of a driven nonlinear microcavity oscillator has been investigated by means of quasi-classical kinetic equations. We show that for coloured, i.e. narrow-band, relatively intense noise, the escape time is controlled by the interplay of two mechanisms: the noise induced drift and adiabatic regular shift of the oscillator state towards unstable saddle point. The cross-over between these mechanisms takes place in a particular range of the driving field intensity values, depending on the ratio between the oscillator damping and the coloured noise spectrum width. The dependence of the transition rate on the noise correlation time is analyzed for wide range of correlation time values. The article is published in the original.     

Color centres and polymorphism in pure WO3 and mixed (1−x)WO3−y·xReO2 powders

The relationship between structural transformations and colour centres creation is discussed for deeply coloured hydrogen tungsten bronzes and for pure WO₃ powders, acquiring less intense colour after mechanical treatments of variable duration. A comparative study on coloration is made also for mixed compounds (1−x)WO_3−y·xReO₂, where an evidence of a resonance effect for a particular Raman band at 970 cm⁻¹, attributed to the color centres, is observed. Besides, it is found that even moderate milling treatments result in a quite different structural evolution of tungsten trioxide upon cooling. Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999.