作者onlyveritas ( 食梦者)
看板Chemistry
标题[问题] 物理化学共轭pi键问题
时间Sun Nov 17 14:25:50 2013
For a linear conjugated polyene with each of N carbon atoms contributing an
electron in a 2p orbital, the energy Ej of the resulting π molecular orbitals
are given by:
Ej=α+2βcos[jπ/(N+1)] j=1,2,3,....N
If α = -13eV and β = -6eV, which is the shortest conjugated carbon chain
molecule capable of absorbing some visible light?
参考答案:
可见光范围最短波长为420nm
代入ΔE=hc/λ
=6.626x10^-34 x 3x10^8 / 420x10^-9 =4.73x10^-19J x 1eV./1.602x10^-19J
=2.954eV
→(2.954/2)/12 = 0.123
即Ej(HOMO)=α+2βx0.123 , Ej+1(LUMO)=α-2βx0.123
..........
我的问题是我不知道(2.954/2)/12 = 0.123这个算式是怎麽来的？
然後为什麽要这麽算？
请版友指正
谢谢
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1F：推 JohnnyDesui:用盒中粒子的En来算？ 11/18 03:21
2F：→ onlyveritas:我是不知道为什麽2.954eV还要除以2再除以12啦.... 11/18 08:33
3F：推 silentfish:12是两倍β,2是三角函数合并後的结果 11/19 09:49
4F：推 o810418:那请问除beta之前的alpha项不用减去吗 11/19 22:36
5F：推 silentfish:ΔE=Ej-Ej-1, α就被减掉了 11/20 08:39