MECHANISM OF SCINTILLATION OF HELIUM, HELIUM--ARGON, AND HELIUM--NEON GAS MIXTURES EXCITED BY ALPHA PARTICLES.
MECHANISM OF SCINTILLATION OF HELIUM, HELIUM--ARGON, AND HELIUM--NEON GAS MIXTURES EXCITED BY ALPHA PARTICLES.
复制标题
由 α 粒子激发的氦、氦-氩和氦-氖气体混合物的闪烁机制。
DOI：
10.1103/physrev.165.225
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发表时间：
1968
期刊：
影响因子：
--
通讯作者：
T. Doke
中科院分区：
文献类型：
--
作者：
S. Kubota;T. Takahashi;T. Doke
对α粒子激发氦、氦-氩和氦-霓离子混合气体的闪烁机理进行了实验研究。当外加电场逐渐增加到Ep∼1.0V/cm Torr时，在低于3atm的压力下，没有观察到光产额的明显下降，其中E是电场，p是气体压力。氦闪烁光的脉冲形状由一个慢分量和一个出现在脉冲前沿的尖峰组成。光强的主要分量由公式EXP(−tτm)−EXP(−tτf)表示，其中t是以秒为单位的时间，τm=10×10−6秒，τf=0.3p−2.2±0.3秒(以Torr为单位)。在这些结果的基础上，得出结论：发射的光子是在一个亚稳态氦原子和两个基态氦原子之间的三体碰撞形成的激发氦分子的衰变过程中释放出来的。在氦的主要部分中含有少量Ar的混合物的光产额显著下降，这可以用亚稳态氦原子产生Ar离子(彭宁过程)来解释。氦中少量的Ne的混合物的同样特征的大降幅似乎是由氦原子到Ne原子的激发转移引起的。在300K下，用三体碰撞产生激发态氦分子的截面σf估计为50×10−23p cm2，其中p为Torr。根据σf的值，分别利用Jesse和Sadoskis估计的σi与σf的比值和Northrop和Gursky的计算结果，计算出氦-Ar彭宁过程的截面密度分别为41×10−16和14×10σ16 cm2。
An experimental investigation of the mechanism of scintillation of helium, helium-argon, and helium-neon mixtures excited by α particles has been performed. No detectable decrease in light yield was observed at pressures less than 3 atm when the applied electric field was increased in steps to E p∼ 1.0 V/cm Torr, where E is the electric field and p is the gas pressure. The pulse shape of helium scintillation light consists of a slow component and a spike appearing on the leading edge of the pulse. The main component of light intensity is represented by the formula exp (− t τ m)− exp (− t τ f), where t is the time in sec, τ m= 10× 10− 6 sec, and τ f= 0.3 p− 2.2±0.3 sec (p in Torr). Most of the emitted photons had a wavelength of less than 1050 ÅA. On the basis of these results, it is concluded that the emitted photons are released in the decay of excited helium molecules formed as a result of a three-body collision between a metastable and two ground-state helium atoms. A characteristic large drop in the light yield for a mixture of a small proportion of argon in a major fraction of helium can be explained by the production of argon ions by metastable helium atoms (Penning process). The same characteristic large drop for a mixture of small concentration of neon in helium seems to be caused by the excitation transfer from helium to neon atoms. The cross section σ f for the formation of an excited helium molecule by a three-body collision is estimated to be 50× 10− 23 p cm 2 at 300 K, where p is in Torr. From the value of σ f, the cross section σ i of the helium-argon Penning process is calculated as 41× 10− 16 and 14× 10− 16 cm 2 by using the ratios of σ i to σ f estimated by Jesse and Sadauskis and by Northrop and Gursky, respectively.