Ultrahigh-resolution Laser Spectroscopy of the S1← S0 Transition of Anthracene Masaaki Baba (Kyoto University) Yosuke Semba Kazuto Yoshida Shunji Kasahara (Kobe University)

Excited-state Dynamics of PAHs τF 100 ns 300 ns 18 ns dissociation ISC T1 fluo. S0 phos. IC S1 abs. IVR S2

Rotationally Resolved Ultrahigh-resolution Spectroscopy Structure ♣Molecular structure by rotational constants ♦Electronic structure by selection rules Dynamics ♥Internal conversion (IC), predissociation by linewidth ♠Intramolecular vibrational redistribution (IVR) by energy shifts ♪Intersystem crossing by Zeeman splitting

Molecular Orbitals of Anthracene ψ47 HOMO ψ48 LUMO ψ49 ψ46 S1 1B2u ψ48 LUMO ψ49 ψ46 S2 1B3u ψ47 HOMO Au B1u B3g B2g

S1 and S2 state of PAHs B3u CI B3u 1Lb S2 B2u 1La S1 S0 HOMO→LUMO +1

S1 and S2 state of PAHs S0 1La S1 S2 1Lb 1La 1Lb 1Lb 1Lb S2 1La 1La S1

Excitation and Dispersed Spectra in a Supersonic Jet

Excited-state Dynamics in Anthracene S. Okajima, B. E. Forch, and E. C. Lim, J. Phys. Chem. 87, 4571 (1983) ☆ Fluorescence lifetime of deuterated anthracene h10 18 ns, d1 9 ns, d8 22 ns, d9 17 ns, d10 4 ns (Inverse deuterium effect on ISC) W. R. Lambert, P. M. Felker, and A. H. Zewail, J. Chem. Phys. 81, 2209 (1984) ☆ Fluorescence lifetime (nonradiative decay rate) Dispersed fluorescence spectrum (IVR) M. Sonnenschein, A. Amirav, and J. Jortner, J. Phys. Chem. 87, 4571 (1983) ☆ Fluorescence quantum yield of anthracenes h10 0.67, d10 0.13 (T2,T3 effect on ISC) V. Bendkowski, E.Heinecke, and A. Hese, J. Chem. Phys. 127, 224306 (2007) ☆ Rotationally resolved spectrum and the Stark effect

Ultrahigh-resolution UV spectroscopy in molecular beam Doubling cavity UV Ring Ti:S Laser PM Photon Counter Magnet ΔE < 0.0001 cm-1 Computer Millenia X CR699-29 Wavetrain Ar + sample Pulse nozzle 150 ℃ A B A: skimmer, φ2 mm B: slit, width 2 mm Etalon Marker Ref:I2 absorption Nd YVO4 Laser Ultrahigh-resolution UV spectroscopy in molecular beam Doubling cavity UV Ring Dye Laser PM Photon Counter Magnet ΔE < 0.0001 cm-1 Computer Millenia X CR699-29 Wavetrain Ar + sample Pulse nozzle 150 ℃ A B A: skimmer, φ1 mm B: slit, width 0.5 mm Etalon Marker Ref: I2 hyperfine Nd YVO4 Laser

S1 ← S0 000 Bands of Anthracene-h10 and d10

Molecular Constants (cm-1) Anthracene-h10 Anthracene-d10 S01Ag(v"=0) S11B1u(v'=0) S01Ag(v"=0) S11B1u(v'=0) A 0.071591 (4) 0.072363(4) 0.060344(7) 0.060950(7) B 0.015095(3) 0.014890(3) 0.013745(4) 0.013561(4) C 0.012477(2) 0.012353(2) 0.011200(2) 0.000095(2) DK (×10-8) -5.3(15) -5.7(14) -2.6(27) -4.1(32) DJK (×10-8) 3.06(93) 3.56(87) -2.6(16) -1.1(16) DJ (×10-9) -3.8(16) -4.3(16) 6.3(32) 4.7(31) K (×10-7) -2.38(64) -2.79(65) J (×10-9) -1.99(78) -2.06(77)  -0.9114 -0.9154 -0.8964 -0.9010  (10-46 kgm2) -0.1798 -0.0078 -0.0998 -0.0338 T0 27687.149(3) 27756.453(3) Fit lines 480 286  0.00043 0.00045

Calculated molecular structure A B C Obs. 0.071591 0.015095 0.012477 Calc. 0.07158 0.01509 0.01246 A B C Obs. 0.072363 0.014890 0.012353 Calc. 0.07294 0.01496 0.01241 MP2 / 6-31G(d,p) RCIS / 6-31++G

S1 ← S0 000 Bands of Anthracene-h10 and d10

Rotational dependence of Zeeman broadening

S B J-L coupling -2Cv Jz Lz Zeeman splittings are the largest at (Electronic Coriolis Interaction) S 2 1 B 3u u -2Cv Jz Lz Lz : z-component of orbital angular momentum of electrons Magnetic moment <S11B2u|mz|S21B3u> mz = - μB Lz M = - J M = + J Γ Zeeman splittings are the largest at J = Kc (Ka=0) and proportional to J.

Excitation and Dispersed Spectra in a Supersonic Jet

Summary Rotationally resolved high-resolution spectra of the S1  S0 transition of anthracene-h10 and -d10 have been observed. The natural linewidth of anthracene-d10 is 0.0015 cm-1 (lifetime 4 ns), which is much larger than that of –h10. The Zeeman splitting is very small both for anthracene-h10 and -d10. The main radiationless process in the S1 state is not ISC to the triplet state, but IC to the ground state.

Direction of the Transition Moment ΔKa = 0, ±2, ・・・ ΔKc = ±1, ±3, ・・・ 1B3u ← S0 1Ag A type 1B2u ← S0 1Ag B type 1B1u ← S0 1Ag C type ΔKa = ±1,±3, ・・・ ΔKc = ±1, ±3, ・・・ ΔKa = ±1,±3, ・・・ ΔKc = ±1, ±3, ・・・ ΔKa = ±1, ±3,・・・ ΔKc = 0, ±2,・・・ ΔKa = ±1, ±3,・・・ ΔKc = 0, ±2,・・・

S11Au(v7=1)←S01Ag Band of Glyoxal

Zeeman Splittings in the 2+,30 line

IVR in the S1 state of Anthracene W. R. Lambert, P. M. Felker , and A. H. Zewail , J. Chem. Phys. 81, 2209 (1984)

Lifetime in the S1 state of Anthracene d10 h10 W. R. Lambert, P. M. Felker , and A. H. Zewail , J. Chem. Phys. 81, 2209 (1984)