化学家成功测量单分子振动_英语科普

化学家成功测量单分子振动

文章来源：未知文章作者：enread 发布时间：2014-08-21 06:39 字体： [大中小]　进入论坛

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For the first time, chemists have succeeded in measuring vibrational² motion of a single molecule³ with a femtosecond（飞秒） time resolution. The study reveals how vibration¹ of a single molecule differs from the behaviour of larger molecular⁴ groups. The study was performed at the University of California, Irvine, where post-doctoral researcher Eero Hulkko from the University of Jyväskylä works as a visiting fellow under professor Vartkess A. Apkarian, whose team participated in the study. The second team was lead by Professor Eric O. Potma. The results of the study made the cover of the August issue of Nature Photonics magazine.

The scientists employed ultra-short femtosecond (10-15 s) laser pulses in the visible light spectrum⁵ to measure the motion of individual molecules⁶.

Seeing a single organic bipyridylethylene (BPE) molecule vibrate as a function of time was possible through the scattering⁷ of the light pulses. The method is known as time-resolved coherent anti-Stokes Raman scattering (tr-CARS).

In conjunction with the study, the scientists developed a new method for identifying single molecules by optical means.

Aided by gold nanoantennas

The observations of single BPE molecule vibrations⁸ was possible using so called "plasmonic nanoantennas," which consist of two gold nanoparticles of approximately 90 nanometres. A nanometre is one billionth of a meter. The nanoantennas amplify⁹ the radiation from a single molecule to a detectable¹⁰ level.

"Detecting one molecule through scattering of light is extremely difficult," says Doctor Hulkko, who participated in the study, "which is why we needed to amplify the signal."

Nanoparticle amplification¹¹ of molecular signals is employed in various spectroscopic（光谱学的） techniques, such as surface-enhanced Raman scattering (SERS), which is used for routine detection of single molecules.

Vibrations in a single molecule are strictly¹² governed by quantum mechanics.. In order to be detectable with the method, a molecule has to be in two (or more) quantum states at once. In quantum mechanics, this is known as coherent superposition of vibrational states -- a wave packet. In molecular groups, the states within the wave packet usually lose their phase correlation¹³ within a short period of time. This is called dephasing（移相，退相位）.

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1 vibration
n.颤动，振动；摆动
参考例句：
There is so much vibration on a ship that one cannot write.船上的震动大得使人无法书写。 The vibration of the window woke me up.窗子的震动把我惊醒了。

2 vibrational
adj.振动的，摇摆的
参考例句：
However, heating energizes the vibrational, rotational, and electronic motions all at once. 但是，加热会一下子把振动、转动和电子运动统统加强。来自英汉非文学 - 科技 Such photons will excite the higher vibrational levels of the OH molecule. 这种光子会激发OH分子的较高振动能级。来自辞典例句

3 molecule
n.分子，克分子
参考例句：
A molecule of water is made up of two atoms of hygrogen and one atom of oxygen.一个水分子是由P妈?f婘??妈?成的。 This gives us the structural formula of the molecule.这种方式给出了分子的结构式。

4 molecular
adj.分子的；克分子的
参考例句：
The research will provide direct insight into molecular mechanisms.这项研究将使人能够直接地了解分子的机理。 For the pressure to become zero, molecular bombardment must cease.当压强趋近于零时，分子的碰撞就停止了。

5 spectrum
n.谱，光谱，频谱；范围，幅度，系列
参考例句：
This is a kind of atomic spectrum.这是一种原子光谱。 We have known much of the constitution of the solar spectrum.关于太阳光谱的构成，我们已了解不少。

6 molecules
分子( molecule的名词复数 )
参考例句：
The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。 Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。

7 scattering
n.[物]散射；散乱，分散；在媒介质中的散播adj.散乱的；分散在不同范围的；广泛扩散的；（选票）数量分散的v.散射(scatter的ing形式)；散布；驱散
参考例句：
The child felle into a rage and began scattering its toys about. 这孩子突发狂怒，把玩具扔得满地都是。来自《简明英汉词典》 The farmers are scattering seed. 农夫们在播种。来自《简明英汉词典》

8 vibrations
n.摆动( vibration的名词复数 )；震动；感受；（偏离平衡位置的）一次性往复振动
参考例句：
We could feel the vibrations from the trucks passing outside. 我们可以感到外面卡车经过时的颤动。 I am drawn to that girl; I get good vibrations from her. 我被那女孩吸引住了，她使我产生良好的感觉。来自《简明英汉词典》

9 amplify
vt.放大，增强；详述，详加解说
参考例句：
The new manager wants to amplify the company.新经理想要扩大公司。 Please amplify your remarks by giving us some examples.请举例详述你的话。

10 detectable
adj.可发觉的；可查明的
参考例句：
The noise is barely detectable by the human ear.人的耳朵几乎是察觉不到这种噪音的。 The inflection point at this PH is barely detectable.在此PH值下，拐点不易发现。

11 amplification
n.扩大，发挥
参考例句：
The voice of despair may be weak and need amplification.绝望的呼声可能很微弱，需要扩大。 Some of them require further amplification.其中有些内容需进一步详细阐明。

12 strictly
adv.严厉地，严格地；严密地
参考例句：
His doctor is dieting him strictly.他的医生严格规定他的饮食。 The guests were seated strictly in order of precedence.客人严格按照地位高低就座。

13 correlation
n.相互关系，相关，关连
参考例句：
The second group of measurements had a high correlation with the first.第二组测量数据与第一组高度相关。 A high correlation exists in America between education and economic position.教育和经济地位在美国有极密切的关系。

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