标题： 非局部辐射转移在强反转激光器中 显示英文标题

标题： Non--local radiative transfer in strongly inverted masers

摘要： 脉泽跃迁在表现出大范围密度和温度的介质中经常被观测到。 它们可以用来获取所观测区域的动力学和物理条件的信息。 为了对脉泽区域中存在的物理条件获得可靠约束，有必要对所观测分子的能量水平的激发机制进行建模。 我们提出了一种数值方法，使我们能够得到统计平衡和辐射转移方程的自洽解。 使用标准脉泽理论，短特征方法被扩展以获得积分微分辐射转移方程的解，适用于强脉泽线的情况。 我们将该方法应用于水分子的脉泽线，并与使用较不精确方法获得的结果进行比较。 在大脉泽光学厚度的范围内，我们发现脉泽线的强度存在很大差异，可能高达几个数量级。 然而，两种方法之间的比较显示，对热线的影响是适度的。 最后，我们讨论了速率系数对水分子脉泽线和光学厚度预测的影响，使用了涉及氦、ortho-H2和para-H2的各种速率系数集。 我们发现，一条线的脉泽性质不受所选碰撞速率的影响。 然而，从一组速率到另一组速率，模拟的线光学厚度和强度可以变化达约2倍和10倍。 显示英文摘要

摘要： Maser transitions are commonly observed in media exhibiting a large range of densities and temperatures. They can be used to obtain information on the dynamics and physical conditions of the observed regions. In order to obtain reliable constraints on the physical conditions prevailing in the masing regions, it is necessary to model the excitation mechanisms of the energy levels of the observed molecules. We present a numerical method that enables us to obtain self-consistent solutions for both the statistical equilibrium and radiative transfer equations. Using the standard maser theory, the method of Short Characteristics is extended to obtain the solution of the integro-differential radiative transfer equation, appropriate to the case of intense masing lines. We have applied our method to the maser lines of the H2O molecule and we compare with the results obtained with a less accurate approach. In the regime of large maser opacities we find large differences in the intensity of the maser lines that could be as high as several orders of magnitude. The comparison between the two methods shows, however, that the effect on the thermal lines is modest. Finally, the effect introduced by rate coefficients on the prediction of H2O masing lines and opacities is discussed, making use of various sets of rate coefficients involving He, o-H2 and p-H2. We find that the masing nature of a line is not affected by the selected collisional rates. However, from one set to the other the modelled line opacities and intensities can vary by up to a factor ~2 and ~10 respectively.