In this study, the effects of electric and tilted magnetic fields on changes in the total absorption coefficient and the refractive index, including the linear and third-order nonlinear terms for transition between the ground and first excited level of an electron confined within the GaAs/GaAlAs quantum well, have been investigated. Furthermore, the effects of the magnetic field direction (i.e., different tilt angles) and the well parameters as well as the electric field strength on the optical properties are taken into consideration. The energy levels and wave functions of the system are calculated by using the effective mass approximation and the compact density-matrix approach is used for optical transitions. The obtained results show that the optical properties of the system are sensitive to the applied external fields and well dimensions.

In the title compound, C 10 H 7 Br 2 NO, the methoxy C atom deviates from the quinoline ring system (r.m.s deviation = 0.003 Å ) by 1.204 (4) Å . In the crystal, C-HÁ Á ÁO hydrogen bonds link the molecules into infinite chains along the baxis direction. Aromatic -stacking interactions [centroid-to-centroid distance = 3.7659 (19) Å ] are also observed. Structure descriptionThe treatment of several dihalogenated quinoline derivatives with NaOMe in basic solutions afforded mono methoxide analogues (Politanskaya et al., 2005). Our own work has studied the bromination reactions of substituted quinolines (Ö kten & Ç akmak, 2015; Ö kten et al., 2015). The present study presents the crystal structure of 5,7-dibromo-8-hydroxyquinoline.In the title compound ( Fig. 1), the Br-C bond lengths are 1.889 (3) and 1.901 (3) Å , and the Br-C-C bond angles vary from 117.6 (2) to 120.2 (2). The relatively wide range of Br-C-C angles may be due to the alternation of the bond-lengths in the bromine-substituted six-membered ring, which vary from 1.357 (4) to 1.425 (4) Å .The packing of the title compound viewed down the b axis is shown in Fig. 2. The crystal structure features C-HÁ Á ÁO hydrogen bonds, which lead to the formation of chains along the b-axis direction (Fig. 3 and Table 1). Furthermore, aromatic -stacking interactions [Cg1Á Á ÁCg2(x, 1 + y, z) = 3.7659 (19) Å ; Cg1 and Cg2 are the centroids of the N1/C1-C5 pyridine and C4-C9 benzene rings, respectively] in the [010] direction are also observed. Keywords: crystal structure; quinoline ring system; hydrogen bonds; -stacking interactions. CCDC reference: 1546956Structural data: full structural data are available from iucrdata.iucr.org data reports Synthesis and crystallization 5,7-Dibromoquinolin-8-ol (1.0 g, 3.3 mmol) was added to a solution of NaOH (132 mg, 3.3 mmol) in distilled water (100 ml). Me 2 SO 4 (416 mg, 3.3 mmol) was added dropwise to the mixture at 263 K for 1 h while being stirred. The mixture was heated to 343-353 K for 1 h. After completion of the reaction (the colour of the mixture changed, 2 h), the solid was dissolved in CHCl 3 (50 ml). The organic layer was successively washed with 10% Na 2 CO 3 (2 Â 15 ml) and 10% NaOH (2 Â 15 ml), dried over Na 2 SO 4 , and the solvent was removed under vacuum. The crude material (2.12 g) was passed through a short alumina column and eluted with EtOAchexane (1:6, 150 ml) to obtain the title compound (1 g, 95%) as colourless needles, m.p. 372-375 K.

In this study, the effects of the external fields (electric and tilted magnetic fields) and well parameters on the optical absorption coefficients in GaAs/GaAlAs multiple (five) quantum wells under the applied electric and tilted magnetic fields has been investigated theoretically. Firstly, the energy eigenvalues and eigen functions of an electron confined in multiple quantum wells are calculated by analytically from Schrödinger equation using the transfer matrix method within the effective mass approximation, Secondly, the linear, nonlinear and total intersubband optical absorptions in GaAs/GaAlAs multiple quantum wells system are studied within the compact density-matrix approach. It is shown that the parameters such as strenghts of the external fields and θtilted angle values not only shift the peak positions in absorption spectrum but also considerably modify their potential heights. In generally, electronic and optical properties of the quantum wells are very sensitive to the applied external fields and well parameters. Therefore, we can conclude that the effect of the external fields can be used to tune and control the optical properties of interest in the range of the far-infrared electromagnetic spectrum.