PMID- 18663218
OWN - NLM
STAT- PubMed-not-MEDLINE
DCOM- 20081006
LR  - 20211020
IS  - 1091-6490 (Electronic)
IS  - 0027-8424 (Print)
IS  - 0027-8424 (Linking)
VI  - 105
IP  - 35
DP  - 2008 Sep 2
TI  - Exploring nuclear motion through conical intersections in the UV 
      photodissociation of phenols and thiophenol.
PG  - 12701-6
LID - 10.1073/pnas.0800463105 [doi]
AB  - High-resolution time-of-flight measurements of H atom products from photolysis of 
      phenol, 4-methylphenol, 4-fluorophenol, and thiophenol, at many UV wavelengths 
      (lambda(phot)), have allowed systematic study of the influence of ring 
      substituents and the heteroatom on the fragmentation dynamics. All dissociate by 
      X-H (X = O, S) bond fission after excitation at their respective 
      S(1)((1)pipi*)-S(0) origins and at all shorter wavelengths. The achieved kinetic 
      energy resolution reveals population of selected vibrational levels of the 
      various phenoxyl and thiophenoxyl coproducts, providing uniquely detailed 
      insights into the fragmentation dynamics. Dissociation in all cases is deduced to 
      involve nuclear motion on the (1)pisigma* potential energy surface (PES). The 
      route to accessing this PES, and the subsequent dynamics, is seen to be very 
      sensitive to lambda(phot) and substitution of the heteroatom. In the case of the 
      phenols, dissociation after excitation at long lambda(phot) is rationalized in 
      terms of radiationless transfer from S(1) to S(0) levels carrying sufficient O-H 
      stretch vibrational energy to allow coupling via the conical intersection between 
      the S(0) and (1)pisigma* PESs at longer O-H bond lengths. In contrast, H + 
      C(6)H(5)O(X(2)B(1)) products formed after excitation at short lambda(phot) 
      exhibit anisotropic recoil-velocity distributions, consistent with prompt 
      dissociation induced by coupling between the photoprepared (1)pipi* excited state 
      and the (1)pisigma* PES. The fragmentation dynamics of thiophenol at all 
      lambda(phot) matches the latter behavior more closely, reflecting the different 
      relative dispositions of the (1)pipi* and (1)pisigma* PESs. Additional insights 
      are provided by the observed branching into the ground (X(2)B(1)) and first 
      excited ((2)B(2)) states of the resulting C(6)H(5)S radicals.
FAU - Ashfold, Michael N R
AU  - Ashfold MN
AD  - School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom. 
      mike.ashfold@bris.ac.uk
FAU - Devine, Adam L
AU  - Devine AL
FAU - Dixon, Richard N
AU  - Dixon RN
FAU - King, Graeme A
AU  - King GA
FAU - Nix, Michael G D
AU  - Nix MG
FAU - Oliver, Thomas A A
AU  - Oliver TA
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20080728
PL  - United States
TA  - Proc Natl Acad Sci U S A
JT  - Proceedings of the National Academy of Sciences of the United States of America
JID - 7505876
PMC - PMC2529099
COIS- The authors declare no conflict of interest.
EDAT- 2008/07/30 09:00
MHDA- 2008/07/30 09:01
PMCR- 2009/03/02
CRDT- 2008/07/30 09:00
PHST- 2008/07/30 09:00 [pubmed]
PHST- 2008/07/30 09:01 [medline]
PHST- 2008/07/30 09:00 [entrez]
PHST- 2009/03/02 00:00 [pmc-release]
AID - 0800463105 [pii]
AID - 3967 [pii]
AID - 10.1073/pnas.0800463105 [doi]
PST - ppublish
SO  - Proc Natl Acad Sci U S A. 2008 Sep 2;105(35):12701-6. doi: 
      10.1073/pnas.0800463105. Epub 2008 Jul 28.