Hyperfine Coupling in Methyl Radical Isotopomers

详细信息    查看全文

• 作者：Iain McKenzie ; Jean-Claude Brodovitch ; Khashayar Ghandi ; Brett M. McCollum ; Paul W. Percival
• 刊名：Journal of Physical Chemistry A
• 出版年：2007
• 出版时间：October 25, 2007
• 年：2007
• 卷：111
• 期：42
• 页码：10625 - 10634
• 全文大小：140K
• 年卷期：v.111,no.42(October 25, 2007)
• ISSN：1520-5215

文摘

The hyperfine coupling constants (hfcs) of two methyl radical isotopomers, CH₂Mu and CD₂Mu, have beenmeasured over a wide range of temperature in ketene and ketene-d₂, from which the radicals were generated.The magnitudes of the hfcs of these muoniated methyl radical isotopomers are larger than those of CH₃ andCD₃ due to larger zero-point energy in the out-of-plane bending mode. In contrast to CH₃ and CD₃, where thecoupling constants become smaller with increasing temperature, the negative hfcs of the muoniated radicalswere found to increase in magnitude (become more negative) with temperature, passing through a maximumnear the boiling point of ketene. This behavior is attributed to a solvent-induced change in the force constantof the out-of-plane bending mode. The opposite temperature effect known for CH₃ and CD₃ is explained byexcitation of the low frequency out-of-plane bending mode. This effect is much smaller in the muoniatedradicals, where the vibrational frequency is significantly higher due to the light mass of muonium; consequently,the solvent effect dominates at low temperatures.