| 词条 | Femtochemistry |
| 释义 |
Application of femtochemistry in biological studies has also helped to elucidate the conformational dynamics of stem-loop RNA structures.[2][3] Many publications have discussed the possibility of controlling chemical reactions by this method,{{clarify|reason=By what method? Femtochemistry may include methods but none have been named or singled out at this point in the narrative.|date=June 2015}} but this remains controversial.[4] The steps in some reactions occur in the femtosecond timescale and sometimes in attosecond timescales,[5] and will sometimes form intermediate products. These reaction intermediates cannot always be deduced from observing the start and end products. Pump–probe spectroscopyThe simplest approach and still one of the most common techniques is known as pump–probe spectroscopy. In this method, two or more optical pulses with variable time delay between them are used to investigate the processes happening during a chemical reaction. The first pulse (pump) initiates the reaction, by breaking a bond or exciting one of the reactants. The second pulse (probe) is then used to interrogate the progress of the reaction a certain period of time after initiation. As the reaction progresses, the response of the reacting system to the probe pulse will change. By continually scanning the time delay between pump and probe pulses and observing the response, workers can reconstruct the progress of the reaction as a function of time. ExamplesFemtochemistry has been used to show the time-resolved electronic stages of bromine dissociation.[6] When dissociated by a 400 nm laser pulse, electrons completely localize onto individual atoms after 140 fs, with Br atoms separated by 6.0 Å after 160 fs. See also
References1. ^The 1999 Nobel Prize in Chemistry, article on nobelprize.org 2. ^{{cite journal | last1 = Kadakkuzha | first1 = B. M. | last2 = Zhao | first2 = L. | last3 = Xia | first3 = T. | year = 2009 | title = Conformational Distribution and Ultrafast Base Dynamics of Leadzyme | url = | journal = Biochemistry | volume = 48 | issue = | pages = 3807–3809 | doi = 10.1021/bi900256q | pmid=19301929}} 3. ^{{cite journal|last1=Lu|first1=Jia|last2=Kadakkuzha|first2=Beena M.|last3=Zhao|first3=Liang|title=Previous Article Next Article Table of Contents Dynamic Ensemble View of the Conformational Landscape of HIV-1 TAR RNA and Allosteric Recognition|journal=Biochemistry|date=2011|volume=50|pages=5042–5057|pmid=21553929|doi=10.1021/bi200495d|display-authors=etal}} 4. ^Femtochemistry. Past, present, and future A.H.Zewail, Pure Appl. Chem., Vol.72, No.12, pp.2219–2231, 2000. 5. ^{{cite journal|last=Kling |first=Matthias F. |author2=Vrakking, Marc J.J. |title=Attosecond Electron Dynamics |journal=Annual Review of Physical Chemistry |date=1 May 2008 |volume=59 |issue=1 |pages=463–492 |doi=10.1146/annurev.physchem.59.032607.093532 |url=http://www.annualreviews.org/doi/10.1146/annurev.physchem.59.032607.093532 |accessdate=31 October 2011 |pmid=18031218|bibcode=2008ARPC...59..463K }} 6. ^{{cite journal|last1=Li|first1=Wen|title=Visualizing electron rearrangement in space and timeduring the transition from a molecule to atoms|journal=PNAS|date=November 23, 2010|volume=107|issue=47|pages=20219–20222|doi=10.1073/pnas.1014723107|url=http://www.pnas.org/content/107/47/20219.abstract|accessdate=12 July 2015|display-authors=etal|pmid=21059945|pmc=2996685|bibcode=2010PNAS..10720219L}} Further reading{{cite book |title=Ultrafast Optics |author=Andrew M. Weiner |url=http://www.wiley.com/WileyCDA/WileyTitle/productCd-0471415391.html |isbn=978-0-471-41539-8 |year=2009 |publisher=Wiley}}
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