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Ultrahigh-resolution Laser Spectroscopy and The Zeeman Effect of Naphthalene S 1 ← S 0 Transition. c ( z ). Kazuto Yoshida , Shunji Kasahara Kobe University, Japan Masaaki Baba Kyoto University, Japan. b ( y ). a ( x ). Introduction. PAHs (Polycyclic Aromatic Hydrocarbons).

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  1. Ultrahigh-resolution Laser Spectroscopy and The Zeeman Effect of Naphthalene S1←S0 Transition c (z) Kazuto Yoshida, Shunji Kasahara Kobe University, Japan Masaaki Baba Kyoto University, Japan b (y) a (x)

  2. Introduction PAHs (Polycyclic Aromatic Hydrocarbons) anthracene naphthalene benzene TG10 TG11 Ultrahigh-resolution laser spectroscopy Molecular Constants Molecular Structure Linewidth Energy Shift Excited-State Dynamics Zeeman Effect

  3. Excited-state dynamics S2 Intramolecular Vibrational Redistribution InterSystem Crossing Internal Conversion IC IVR ISC S1 T1 Naphthalene ΦF=0.4 fluorescence absorption phosphorescence [ F. M. Behlen, S. A. Rice, J. Chem. Phys. 75, 5672 (1981) ] S0

  4. Electronic states : Molecular orbitals ψ36 b3g ψ36 b3g LUMO LUMO ψ35 b2g ψ35 b2g B3u B2u HOMO HOMO au au ψ34 ψ34 b1u b1u ψ33 ψ33

  5. Electronic state Fluorescence excitation spectrum in a supersonic jet HOMO-1→LUMO HOMO→ LUMO+1 S31B3u S2←S0 1B3u 1La 1B2u S21B2u 1Lb S1←S0 weak S11B3u HOMO→LUMO S01Ag [ S. M. Beck et al., J. Chem. Phys. 73, 2019 (1980) ] S1←S0 HOMO-1→LUMO HOMO→ LUMO+1 TG11 S31B3u 1B3u 1Lb S2←S0 weak (NOT FOUND) S21B3u 1La 1B2u S11B2u HOMO→LUMO S01Ag RELATIVE FREQUENCY (CM-1)

  6. High-resolution spectrum S1←S0 transition ag vibration b1g vibration Resolution : 0.2 cm-1 435 1422 1380 1390 1432 910 2122 2410 000 2570 Wavenumber / cm-1

  7. Sensitized phosphorescence excitation spectrum 1390 Fluorescence excitation spectrum 1380 Sensitized phosphorescence excitation spectrum [T. Suzuki et al., Chem. Phys. Lett. 127, 292(1986)]

  8. Experimental setup Calibration of absolute wavenumber I2 stabilized Etalon Marker Single-mode laser Ref: I2 hyperfine (accuracy ：0.0001 cm-1) Ring Dye Laser Nd : YVO4 Laser Doubling cavity Millennia Xs CR699-29 dye:R6G Wavetrain Molecular Beam linewidth ：2 MHz A B Magnet Pulse nozzle Ar + sample 100 ℃ Computer Photon Filter Counter PM A: skimmer φ2 mm B: slit width 1.5 mm UV

  9. Observed spectra ultrahigh-resolution spectrum of naphthalene accuracy : 0.0002 cm-1 600 MHz etalon marks 33396.7765 cm-1 Doppler-free saturation spectrum of I2 Wavenumber / cm-1

  10. Ultrahigh-resolution spectra band origin 000+1380 cm-1 band rP pP rR pR b-type qR qP qQ 000+1390 cm-1 band a-type Wavenumber / cm-1

  11. Ultrahigh-resolution spectrum of 000+1380 cm-1 band Ka Ka Wavenumber / cm-1

  12. Molecular constants

  13. Ultrahigh-resolution spectra band origin 000+1380 cm-1 band b-type a-type 000+1390 cm-1 band Wavenumber / cm-1

  14. Comparison between observed and calculated spectrum Ka 000+1380 cm-1 band Ka obs. calc. Wavenumber / cm-1

  15. Ultrahigh-resolution spectra band origin 000+1380 cm-1 band b-type a-type 000+1390 cm-1 band Wavenumber / cm-1

  16. Comparison between observed and calculated spectrum 000+1390 cm-1 band obs. calc. Wavenumber / cm-1

  17. Energy shifts of 000+1390 cm-1 band ΔE / cm-1 Ka=0 Ka=1 Ka=2 Upper J ΔE=Eobs. - Ecalc. Eobs. : observed transition energy Ecalc. : calculated transition energy

  18. The Zeeman Effect

  19. High-resolution spectrum S1←S0 transition We observed the Zeeman effect for rotationally resolved spectra 435 1380 1390 1422 1432 910 2122 2410 000 2570 Wavenumber / cm-1

  20. Zeeman splitting of 000+435 cm-1 band c (z) High Ka low Ka b (y) m a (x) H=0 T magnetic moment H=0.50 T Wavenumber / cm-1

  21. J-dependence of Zeeman splitting 000+435 cm-1 band 000+1422 cm-1 band Kc= J (Ka= 0) Kc= J (Ka= 0) ZS / cm-1 ZS / cm-1 H=0.25 T H=0.46 T H=0.50 T H=0.90 T J J

  22. J-L coupling (electronic Coriolis interaction) JK-dependence can be well explained by J-Lcoupling Magnetic moment in S11B3u state comes from J-L coupling between S11B3u and S21B2ustates. The magnitude of Zeeman Splitting (ZS) is S21B2u -2 Jz Lz S11B3u （comparison between observed and calculated ZS） ZS of rP0(28) line (J=28, Kc=28) in 000+435 cm-1 band Observed ZS 0.0010 cm-1 Calculated ZS 0.0011 cm-1

  23. Zeeman splitting of 000+1390 cm-1 band H=0 T H=0.27 T Wavenumber / cm-1

  24. Summary We observed ultrahigh-resolution spectra of 000+1380 cm-1 and 000+1390 cm-1 vibronic bands of naphthalene S1←S0 transition. Several rotational lines of these vibronic bands were assigned and the rotational constants were determined in high accuracy. We determined vibrational energy of v4, v13 in high accuracy. In 000+1390 cm-1 band , the local energy shifts were found. The Zeeman splittingwas very small and was proportional to J for a given K. The magnetic moment comes from an electron angular momentum induced by the J-L coupling between S11B3u and S21B2u states. The main nonradiative process of S1 state is not intersystem crossing to the triplet state. It is presumed to be internal conversion to ground state.

  25. Rotational counter band origin transition moment long axis a-type transition moment short axis b-type transition moment out of plane c-type Wavenumber / cm-1

  26. Zeeman interaction Matrix element of Zeeman interaction Magnetic moment is along to out of plane. M =- J M =+ J ZS The magnitude of Zeeman spliiting (ZS) is

  27. JK-dependence of Zeeman splitting naphthalene-d8 K-dependence J-dependence

  28. v-dependence of Zeeman splitting at Ka=0 (Kc=J), J=20, H = 0.2 T Zeeman Splitting / MHz ZS is not v-dependence Excess Energy / cm-1

  29. Zeeman Splitting of glyoxal

  30. El-sayed rule Spin-orbit Interaction 1ππ* 3ππ* 3nπ* 1nπ*

  31. n n Excited states of glyoxal ππ* S31Bu nπ* S21Ag ππ* nπ* HSO T23Bu 71 a l ·s S11Au Hvibronic nπ* T13Au S01Ag

  32. Energy shifts ΔE ΔE=Eobs.－Ecal. Coriolis interaction; parallel: proportional to K, perpendicular: proportional to [J(J+1)－(K±1)]1/2

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