Radio recombination lines from the largest bound atoms in space
Radio recombination lines from the largest bound atoms in space
复制标题
空间中最大束缚原子的无线电重组线
DOI：
10.1111/j.1365-2966.2006.11190.x
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发表时间：
2006
影响因子：
4.8
通讯作者：
India.
中科院分区：
文献类型：
--
作者：
S. Stepkin;A. Konovalenko;N. Kantharia;N. Astronomy;Kharkov;UK Harvard;Pune;I. R. Institute;Bangalore;India.
在这篇文章中，我们报告了在26 MHz附近探测到的一系列由空间中探测到的最大结合碳原子引起的吸收中的无线电重组线(RRL)。这些原子比基态原子大一百万倍以上，在超新星残骸仙后座A(Cas A)前面英仙座臂上的冷薄介质中正在经历三角洲相变(n∼1009，An=4)。理论估计表明，在稀薄介质中重新结合的原子在∼1500时的量子能级是稳定的。我们的数据表明，我们已经探测到原子在非常接近这个理论极限的状态下发出的辐射。我们还报告了在同一云中碳原子的a、β和y跃迁的高信噪比检测。在这些数据中，我们发现，由于压强和辐射加宽导致的线宽随量子数(近似与n5成正比)的增加要比现有假定为幂函数背景辐射场的模型所预期的要温和得多。早些时候也注意到了这种差异。由于忽略了Cas A的低频辐射场的翻转，模型线宽被高估了。在本文中，我们表明，一旦在模型中考虑了光谱周转，就可以自然地解释线宽随量子数的缓慢增长。
In this paper, we report the detection of a series of radio recombination lines (RRLs) in absorption near 26 MHz arising from the largest bound carbon atoms detected in space. These atoms, which are more than a million times larger than the ground-state atoms, are undergoing delta transitions (n ∼ 1009, An = 4) in the cool tenuous medium located in the Perseus arm in front of the supernova remnant, Cassiopeia A (Cas A). Theoretical estimates had shown that atoms which recombined in tenuous media are stable up to quantum levels n ∼ 1500. Our data indicate that we have detected radiation from atoms in states very close to this theoretical limit. We also report high signal-to-noise ratio detections of a, β and y transitions in carbon atoms arising in the same clouds. In these data, we find that the increase in linewidths with quantum number (approximately proportional to n 5 ) due to pressure and radiation broadening of lines is much gentler than that expected from existing models which assume a power-law background radiation field. This discrepancy had also been noted earlier. The model linewidths had been overestimated since the turnover in radiation field of Cas A at low frequencies had been ignored. In this paper, we show that, once the spectral turnover is included in the modelling, the slower increase in linewidth with quantum number is naturally explained.