二極性ヒドロキシル基の蒸発による冷却
Benjamin K Stuhl1, Matthew T Hummon, Mark Yeo
1JILA, National Institute of Standards and Technology and University of Colorado, Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.
Nature
|December 22, 2012
まとめ
研究者は,ヒドロキシル分子のマイクロ波強制蒸発冷却を達成しました. この突破により,超冷たい分子ガスの温度が著しく低下し,相空間密度が増加する.
科学分野:
- 原子物理学 原子物理学とは
- 分子物理学 分子物理学
- 量子化学は量子化学である
背景:
- 強制蒸発冷却は原子物理学に革命を起こし,ボゼ・アインシュタイン凝縮物と超冷たい量子ガスを可能にしました.
- 寒い分子ガスは,電極二極の瞬間によってユニークな性質を備えているが,蒸発による冷却は難解である.
- 課題には,不利な分散比率と,閉じ込められた分子種における遅い熱化が含まれます.
研究 の 目的:
- 中性分子の蒸発冷却を実現するために.
- 分子ガスの温度減少と相空間密度の増加を顕著に示すために.
- 二極分子システムにおける量子変性への道を開くために.
主な方法:
- スターク減速ヒドロキシル (OH(•)) 分子を高梯度磁気四極トラップに負荷する.
- マイクロウェーブによる強制蒸発式冷却の導入.
- 温度と相空間密度を測定するためのスペクトロスコーピック温度計.
主要な成果:
- 中性ヒドロキシル分子の蒸発による冷却が実証されている.
- 温度を少なくとも 1 桁の減少を達成しました.
- 位相空間密度が3桁増加した.
結論:
- マイクロ波による強制蒸発による冷却は,中性分子でも実現可能になりました.
- このテクニックは,相空間密度を大幅に高め,量子退化に接近します.
- 超冷たい二極気体やシンパティック冷却アプリケーションの可能性を開きます.
関連する概念動画
00:54Radical Formation: Homolysis
A bond is formed between two atoms by sharing two electrons. When this bond is broken by supplying sufficient energy, either two electrons can be taken up by one atom forming ions by the cleavage called heterolysis, or the two electrons are shared by two atoms, with one each creating radicals by the cleavage called homolysis.
02:04Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol.
00:51Radical Formation: Elimination
Another method of radical formation is the elimination process. It is the opposite of the addition route and is driven by the instability of the radical. For example, as depicted in Figure 1, dibenzoyl peroxide yields a pair of unstable radicals upon homolysis. Given its instability, this radical spontaneously undergoes elimination via a C–C bond cleavage to form a relatively more stable phenyl radical. The mechanism involves cleavage of the bond between the α and β positions with respect to...
01:17Radical Anti-Markovnikov Addition to Alkenes: Mechanism
The reaction of hydrogen bromide with alkenes in the presence of hydroperoxides or peroxides proceeds via anti-Markovnikov addition. The radical chain reaction comprises initiation, propagation, and termination steps.
The mechanism starts with chain initiation, which involves two steps. In the first chain initiation step, a weak peroxide bond is homolytically cleaved upon mild heating to form two alkoxy radicals. In the second initiation step, a hydrogen atom is abstracted by the alkoxy radical...
The mechanism starts with chain initiation, which involves two steps. In the first chain initiation step, a weak peroxide bond is homolytically cleaved upon mild heating to form two alkoxy radicals. In the second initiation step, a hydrogen atom is abstracted by the alkoxy radical...
03:08Hydroboration-Oxidation of Alkenes
In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.
01:11Radical Reactivity: Overview
Radicals, the highly reactive species, gain stability by undergoing three different reactions. The first reaction involves a radical-radical coupling, in which a radical combines with another radical, forming a spin‐paired molecule. The second reaction is between a radical and a spin‐paired molecule, generating a new radical and a new spin‐paired molecule. The third reaction is radical decomposition in a unimolecular reaction, forming a new radical and a spin‐paired molecule. These three...