title: Delayed dissociation of photoexcited porphyrin cations in a storage ring: determination of triplet quantum yields.
abstract: A technique is described wherein substituent-dependent excited-state properties of gas-phase porphyrins can be accurately quantified. Dissociation lifetimes of photoexcited porphyrin cations were measured in an electrostatic ion storage ring. From these data, upper limits for the triplet quantum yield of the following protonated porphyrins were obtained: protoporphyrin IX (0.63 +/- 0.04), tetraphenylporphyrin (0.73 +/- 0.03), tetra(p-methylphenyl)porphyrin (0.75 +/- 0.03), and tetra(p-cyanophenyl)porphyrin (0.71 +/- 0.03). The values compare well with those for porphyrins in solution.
authors.affiliation: Polymer Department, Risø National Laboratory, Frederiksborgvej 399, DK-4000 Roskilde, Denmark.
authors.forename: Christian B
authors.initials: CB
authors.lastname: Nielsen
authors.forename: James S
authors.initials: JS
authors.lastname: Forster
authors.forename: Peter R
authors.initials: PR
authors.lastname: Ogilby
authors.forename: Steen Brøndsted
authors.initials: SB
authors.lastname: Nielsen
mesh_terms: D002412:Cations; D002627:Chemistry, Physical / Q000379:methods*; D006371:Helium / Q000737:chemistry; D007477:Ions; D008027:Light; D008956:Models, Chemical; D010100:Oxygen / Q000737:chemistry; D010777:Photochemistry / Q000379:methods; D017785:Photons; D011166:Porphyrins / Q000737:chemistry*; D011789:Quantum Theory; D026082:Singlet Oxygen / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D013997:Time Factors
chemical_list: D002412:Cations; D007477:Ions; D011166:Porphyrins; D026082:Singlet Oxygen; D006371:Helium; D010100:Oxygen