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首页> 外文期刊>Philosophical magazine, B. Physics of condensed matter, electronic, optical, and magnetic properties >Vacancy formation energies and mechanisms of ion-molecule reactions from ionic sublimation measurements on potassium bromide single crystals
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Vacancy formation energies and mechanisms of ion-molecule reactions from ionic sublimation measurements on potassium bromide single crystals

机译：溴化钾单晶上离子升华测量的空位形成能和离子分子反应机理

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Using the mass spectrometry technique to study the ionic sublimation of a potassium bromide single crystal, a novel method of determination of the sign of surface charge and of the vacancy formation energies is proposed. It is found that a potassium bromide single crystals, when heated above 600 K, emit positive ionst K+, K-2(+), K2Br+ and K3Br2+. The temperature dependence of thermal ion currents, In I-i - 1/T, measured over the interval 600-920 K exhibited a successive maximum and a minimum with increasing temperature. The extrema are identified with the change in the electrical surface properties. It is inferred that in the intrinsic temperature range the sign of the surface charge for KBr is negative. Locating the temperature at which the surface potential has its maximum positive magnitude enables the free energy g of formation of cation vacancies and the free energy g(+) of formation of anion vacancies to be evaluated at T = 800 K, g(-) = 0.96 +/- 0.03 eV and g(+) = 0.90 +/- 0.03 eV. The relative current intensities are observed to change drastically upon reversal of the surface charge polarity. The mechanisms of formation of K-2(+) and K2Br+ ions are discussed. The influence of the surface charge on the rates of ion-molecule reactions is analysed. [References: 27]
机译：利用质谱技术研究了溴化钾单晶的离子升华，提出了一种测定表面电荷符号和空位形成能的新方法。发现溴化钾单晶在加热到600 K以上时会发出正离子K +，K-2（+），K2Br +和K3Br2 +。在600-920 K的时间间隔内测得的热离子电流的温度依从性（I-i-1 / T）在温度升高时呈现出连续的最大值和最小值。极值由电表面特性的变化确定。可以推断，在固有温度范围内，KBr的表面电荷符号为负。确定表面电势具有最大正振幅的温度，可以评估在T = 800 K时形成阳离子空位的自由能g和在阴离子空位形成时的自由能g（+），T = 800 K，g（-）= 0.96 +/- 0.03 eV和g（+）= 0.90 +/- 0.03 eV。观察到相对电流强度在表面电荷极性反转时急剧变化。讨论了K-2（+）和K2Br +离子的形成机理。分析了表面电荷对离子分子反应速率的影响。 [参考：27]

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