On the Intrinsic Population of the Lowest Triplet State of Thymine

详细信息    查看全文

• 作者：Juan Jos&eacute ; Serrano-P&eacute ; rez ; Remedios Gonzá ; lez-Luque ; Manuela Merchá ; n ; Luis Serrano-Andr&eacute ; s
• 刊名：Journal of Physical Chemistry B
• 出版年：2007
• 出版时间：October 18, 2007
• 年：2007
• 卷：111
• 期：41
• 页码：11880 - 11883
• 全文大小：101K
• 年卷期：v.111,no.41(October 18, 2007)
• ISSN：1520-5207

文摘

The population of the lowest triplet state of thymine after near-UV irradiation has been established, on thebasis of CASPT2//CASSCF quantum chemical calculations, to take place via three distinct intersystem crossingmechanisms from the initially populated singlet bright ¹* state. Two singlet-triplet crossings have beenfound along the minimum-energy path for ultrafast decay of the singlet state at 4.8 and 4.0 eV, involving thelowest ³n* and ³* states, respectively. Large spin-orbit coupling elements predict efficient intersystemcrossing processes in both cases. Another mechanism involving energy transfer from the lowest ¹n* statewith much larger spin-orbit coupling terms can also be proposed. The wavelength dependence measured forthe triplet quantum yield of pyrimidine nucleobases is explained by the location and accessibility of thesinglet-triplet crossing regions.