Plasma formation and temperature measurement during single-bubble cavitation
Plasma formation and temperature measurement during single-bubble cavitation
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DOI：
10.1038/nature03361
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发表时间：
2005-03-03
期刊：
影响因子：
64.8
通讯作者：
Suslick, KS
中科院分区：
文献类型：
--
作者：
Flannigan, DJ;Suslick, KS
单气泡声致发光（SBSL 1 -5）是由气泡压缩过程中达到的极端温度和压力引起的;计算预测（6，7）存在热的、光学不透明的等离子体核（8），随之产生韧致辐射（9，10）。最近有争议的报告（11，12）声称在声空化（11，12）期间观察到来自氘-氘聚变的中子。然而，以前一直没有强有力的实验证据，在单泡或多泡声致发光的等离子体的存在。SBSL通常产生无特征的发射光谱（13），其很少揭示腔内物理条件或化学过程。在这里，我们报告的原子（Ar）发射和广泛的分子（SO）和离子（O-2（+））的进展SBSL光谱从浓H2SO 4水溶液的观察。Ar和SO发射都允许光谱温度测定，如用其他发射体（14-16）实现的多泡声致发光。从Ar和O-2（+）中观察到的发射激发态与任何热过程都不一致。所涉及的Ar激发态具有极高的能量（> 13 eV），并且在测量的Ar发射温度（4，000 - 15，000 K）下不能热填充; O-2的电离能是其键离解能的两倍以上，因此O-2（+）同样不能热产生。因此，我们的结论是，这些发射物种必须起源于碰撞高能电子，离子或粒子从热等离子体核心。
Single-bubble sonoluminescence (SBSL1-5) results from the extreme temperatures and pressures achieved during bubble compression; calculations have predicted(6,7) the existence of a hot, optically opaque plasma core(8) with consequent bremsstrahlung radiation(9,10). Recent controversial reports(11,12) claim the observation of neutrons from deuterium - deuterium fusion during acoustic cavitation(11,12.) However, there has been previously no strong experimental evidence for the existence of a plasma during single- or multi-bubble sonoluminescence. SBSL typically produces featureless emission spectra(13) that reveal little about the intra-cavity physical conditions or chemical processes. Here we report observations of atomic (Ar) emission and extensive molecular (SO) and ionic (O-2(+)) progressions in SBSL spectra from concentrated aqueous H2SO4 solutions. Both the Ar and SO emission permit spectroscopic temperature determinations, as accomplished for multi-bubble sonoluminescence with other emitters(14-16). The emissive excited states observed from both Ar and O-2(+) are inconsistent with any thermal process. The Ar excited states involved are extremely high in energy (> 13 eV) and cannot be thermally populated at the measured Ar emission temperatures (4,000 - 15,000 K); the ionization energy of O-2 is more than twice its bond dissociation energy, so O-2(+) likewise cannot be thermally produced. We therefore conclude that these emitting species must originate from collisions with high-energy electrons, ions or particles from a hot plasma core.