LOW-TEMPERATURE SPECTROSCOPY OF THE 12C2H2 (υ1 + υ3) BAND IN A HELIUM BUFFER GAS
LOW-TEMPERATURE SPECTROSCOPY OF THE 12C2H2 (υ1 + υ3) BAND IN A HELIUM BUFFER GAS
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DOI：
10.1088/0004-637x/801/1/50
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发表时间：
2015-03-01
影响因子：
4.9
通讯作者：
De Natale, P.
中科院分区：
文献类型：
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作者：
Santamaria, L.;Di Sarno, V.;De Natale, P.
用He-4气体冷却缓冲气体，在低温下对(C2H2)-C-12(upsilon(1)+upsilon(3))带进行了激光吸收光谱研究。首先进行了多普勒测温，从记录的光谱中提取平移温度。然后，通过将Boltzmann分布与几条转动振动线的相对强度进行拟合，得到了低至20K的转动温度。我们的设置也证明了调节平移和转动自由度之间的热平衡的潜力。这可以用来以受控的方式重现星际介质中通常遇到的非局部热平衡状态。还讨论了与行星大气建模相关的氦-乙炔碰撞物理基础。特别是，(C2H2)-C-12在缓冲池中的扩散时间是在两个不同的平移温度下相对于He-4通量测量的；然后将观察到的行为与蒙特卡罗模拟预测的行为进行比较，从而提供对各自总弹性截面的估计：Sigma(El)(100K)=(4+/-1)x 10(-20)m(2)和sigma(El)(25K)=(7+/-2)x 10(-20)m(2)。
Buffer gas cooling with a He-4 gas is used to perform laser-absorption spectroscopy of the (C2H2)-C-12 (upsilon(1) + upsilon(3)) band at cryogenic temperatures. Doppler thermometry is first carried out to extract translational temperatures from the recorded spectra. Then, rotational temperatures down to 20 K are retrieved by fitting the Boltzmann distribution to the relative intensities of several ro-vibrational lines. The potential of our setup to tune the thermal equilibrium between translational and rotational degrees of freedom is also demonstrated. This can be used to reproduce in a controlled way the regime of non-local thermal equilibrium typically encountered in the interstellar medium. The underlying helium-acetylene collisional physics, relevant for modeling planetary atmospheres, is also addressed. In particular, the diffusion time of (C2H2)-C-12 in the buffer cell is measured against the He-4 flux at two separate translational temperatures; the observed behavior is then compared with that predicted by a Monte Carlo simulation, thus providing an estimate for the respective total elastic cross sections: sigma(el)(100 K) = (4 +/- 1) x 10(-20) m(2) and sigma(el)(25 K) = (7 +/- 2) x 10(-20) m(2).