论文标题
通过与para-h2碰撞对一氧化氮激发的精细和超精细激发
Fine and hyperfine excitation of nitric oxide by collision with para-H2
论文作者
论文摘要
一氧化氮是在星际培养基中大量检测到的开放壳分子。对其辐射和碰撞过程的精确建模为精确估计其丰度开辟了道路。在这里，我们使用最近开发的准确的相互作用电位，在星际培养基中与最普遍的碰撞伴侣（$ para $ -h $ _2 $ hydrogen Molecules）相撞，以与最普遍的碰撞伴侣发生碰撞，以对NO进行细精和超精细（DE-）激发的第一级系数。我们报告了涉及前74个罚款水平的过渡和相应的442个属于$ f_1 $和$ f_2 $ spin-orbit歧管的量子散射计算。为此，我们已经通过量子机械关闭耦合来计算横截面，最高可达1000 cm $^{ - 1} $的总能量和速率系数为5到100 k。讨论了倾向规则，并根据缩放的No-He速率讨论了新的No-H $ _2 $速率。两组速率系数之间观察到很大的差异，该比较表明，新的碰撞速率必须用于解释无发射线。我们还通过对两条NO线的激发和亮度温度进行辐射转移计算，以150.176和250.4368 GHz进行辐射转移计算，从而检查了这些新速率对冷云中NO激发的影响。这表明，对于典型条件，该物种无法实现局部热力学平衡。我们期望使用本研究中提出的利率来改善对NO的丰度的约束。
Nitric oxide is an open-shell molecule abundantly detected in the interstellar medium. A precise modeling of its radiative and collisional processes opens the path to a precise estimate of its abundance. We present here the first rate coefficients for fine and hyperfine (de-)excitation of NO by collisions with the most ubiquitous collision partner in the interstellar medium, $para$-H$_2$ hydrogen molecules, using a recently developed accurate interaction potential. We report quantum scattering calculations for transitions involving the first 74 fine levels and the corresponding 442 hyperfine levels belonging to both $F_1$ and $F_2$ spin-orbit manifolds. To do so, we have calculated cross sections by means of the quantum mechanical close-coupling approach up to 1000 cm$^{-1}$ of total energy and rate coefficients from 5 to 100 K. Propensity rules are discussed and the new NO-H$_2$ rates are compared to those available in the literature, based on scaled NO-He rates. Large differences are observed between the two sets of rate coefficients, and this comparison shows that the new collision rates must be used in interpreting NO emission lines. We also examined the effect of these new rates on the NO excitation in cold clouds by performing radiative transfer calculations of the excitation and brightness temperatures for the two NO lines at 150.176 and 250.4368 GHz. This shows that the local thermodynamic equilibrium is not fulfilled for this species for typical conditions. We expect the use of the rates presented in this study to improve the constraints on the abundance of NO.
