ULTRAHIGH-RESOLUTION SPECTROSCOPY OF DIBENZOFURAN S 1 ←S 0 TRANSITION SHUNJI KASAHARA 1, Michiru Yamawaki 1, and Masaaki Baba 2 1) Molecular Photoscience Research Center, Kobe University, Japan 2) Graduate School of Science, Kyoto University, Japan J K c(z)c(z) J KcKc c a oblate symmetric top A=B>C b(z)b(z) near prolate asymmetric top A>B ~ C J KcKc a(z)a(z) b c

Motivation for the Measurement of Excited States by Doppler-Free / Sub-Doppler High Resolution Spectroscopy Rotational-resolved high-resolution spectrum in UV-VIS region Regularity of rotational lines  Molecular constants in high accuracy Anomalies of rotational lines  Line position (energy shift)  Line width (broadening)  Zeeman effect (splitting) Assignments of rotational transitions Molecular structure Dynamical process

Nd:YVO 4 Laser; Millenia Xs Magnet Ar gas Pulse nozzle Sample Filter UV laser Etalon marker PD I 2 cell Lock-in Amp. EOM PD Skimmer Slit(1 mm) Vac. pump PM Ring Dye Laser; CR UV Laser  Molecular Beam Single-mode Laser Absolute Wavenumber Measurement System Doubling Cavity; WavetrainSC Computer Photon Counter Accuracy cm -1   cm -1 Ultrahigh-resolution UV spectroscopy in molecular beam Liq. N 2 Trap  (FWHM)  cm -1

Etalon PBS PD λ/4 PZT YAG Laser Error Signal Generator 19MHz Oscillator EOM PBS Error Signal Generator 19MHz Oscillator I 2 stabilized YAG laser I 2 Cell PD PBS PC Stabilized Etalon EOM PD Laser EOM 30MHz Oscillator Frequency Marker (each 30 MHz)

Nd:YVO 4 Laser; Millenia Xs Magnet Ar gas Pulse nozzle Sample Filter UV laser Etalon marker PD I 2 cell Lock-in Amp. EOM PD Skimmer Slit(1 mm) Vac. pump PM Ring Dye Laser; CR UV Laser  Molecular Beam Single-mode Laser Absolute Wavenumber Measurement System Doubling Cavity; WavetrainSC Computer Photon Counter Accuracy cm -1   cm -1 Ultrahigh-resolution UV spectroscopy in molecular beam Liq. N 2 Trap  (FWHM)  cm -1

Chopper PBS: Polarization Beam splitter I 2 Cell PBS Laser Photo -diode Photo -diode Doppler-free absorption spectrum of I 2 Absolute wavenumber of each I 2 hyperfine line can be obtained from “Doppler-free High Resolution Spectral Atlas of Iodine Molecule to cm -1 ” in accuracy of cm -1.

Nd:YVO 4 Laser; Millenia Xs Magnet Ar gas Pulse nozzle Sample Filter UV laser Etalon marker PD I 2 cell Lock-in Amp. EOM PD Skimmer Slit(1 mm) Vac. pump PM Ring Dye Laser; CR UV Laser  Molecular Beam Single-mode Laser Absolute Wavenumber Measurement System Doubling Cavity; WavetrainSC Computer Photon Counter Accuracy cm -1   cm -1 Ultrahigh-resolution UV spectroscopy in molecular beam Liq. N 2 Trap  (FWHM)  cm -1

PM Magnet Laser A A B B Skimmer Pulse nozzle Sample Pole peace Slit Molecular Beam Liq. N 2 trap

Marker etalon (stabilized by I 2 stabilized YAG laser) Doppler-free absorption spectrum of I 2 Rotational-resolved high-resolution spectrum of Dibenzofuran Ultrahigh-resolution spectrum of cm -1 band

S 1 ←S 0 spectrum of dibenzofuran in a molecular beam (resolution : 0.2 cm -1 ) dibenzofuran

Ultrahigh-resolution spectrum of and cm -1 band B-type transition A-type transition

Ψ 47 B1B1 Ψ 46 Ψ 45 Ψ 44 A2A2 B1B1 A2A2 Ψ 43 B1B1 Ψ 42 A2A2 HOMO LUMO 2 nd LUMO 2 nd HOMO 34087(+443 cm -1 ) 1A11A1 1 A 1 ( S 0 ) 1 B 2 ( S 2 ) 1 A 1 ( S 1 ) H vibronic A-type ΔK a = 0 B-type ΔK a =±1 E (cm -1 ) HOMO － LUMO Electronic excited states of dibenzofuran molecule y(a)y(a) z(b)z(b) O

Ultrahigh-resolution spectrum of and cm -1 band

Ultrahigh-resolution spectrum of band (P lines)

Obtained Molecular Constants of S 1 and S 0 States of dibenzofuran S 0 1 A 1 (v=0)S 1 1 A 1 (v=0) A (cm -1 ) (10) (81) B (65) (29) C (57) (17) D K (×10 -8 )3.67(22)3.33(19) D JK (×10 -8 )-3.43(15)-3.328(70) D J (×10 -9 )5.20(27)5.374(88) δ K (×10 -7 )3.26(11)3.106(21) δ J (×10 -9 )1.79(13)2.102(49) κ I a (× kg m 2 ) IbIb IcIc ⊿ = I c - I a - I b T 0 (cm -1 ) (66) standard deviation fitted lines-4835 lines assigned lines-5032 lines band type -B type

Ultrahigh-resolution spectrum of and cm -1 band

Ultrahigh-resolution spectrum of cm -1 band (Q lines)

S 1 ←S 0 spectrum of dibenzofuran in a molecular beam (resolution : 0.2 cm -1 ) dibenzofuran

Ultrahigh-resolution spectrum of higher vibrational band

Obtained Molecular Constants of S 1 and S 0 States of dibenzofuran S 0 1 A 1 (v=0)S 1 1 A 1 (v=0) S 1 1 A 1 (b 2 :v 55 =1) ( cm -1 ) S 1 1 A 1 ( cm -1 ) S 1 1 A 1 ( cm -1 ) S 1 1 A 1 ( cm -1 ) A (cm -1 ) (10) (81) (55) (95) (15) (53) B (65) (29) (25) (28) (50) (51) C (57) (17) (20) (15) (27) (26) D K (×10 -8 )3.67(22)3.33(19)3.24(12)3.12(20)-2.81(41) D JK (×10 -8 )-3.43(15)-3.328(70)-3.099(58)-3.224(71) (78) D J (×10 -9 )5.20(27)5.374(88)4.826(82)5.763(61)-5.83(21) δ K (×10 -7 )3.26(11)3.106(21)2.976(27)3.474(16)-2.830(52) δ J (×10 -9 )1.79(13)2.102(49)1.628(57)1.964(34)-2.24(12) κ I a (× kg m 2 ) IbIb IcIc ⊿ = I c - I a - I b T 0 (cm -1 ) (66) (52) (82) (13) (98) standard deviation fitted lines-4835 lines2904 lines2449 lines135 lines999 lines assigned lines-5032 lines3047 lines2529 lines140 lines1048 lines band type -B typeA type

Zeeman broadening of band

ZS ∝ K c 2 ZS ∝ J 2 K c = 0 （ K a = J ） K c = J （ K a = 0 ） J c KcKc a m Magnetic moment is along to c-axis. (out of plane) (J, K) dependence of the observed Zeeman splittings ZS -MJ-MJ MJMJ

J K c(z)c(z) J KcKc a b(z)b(z) J KcKc a(z)a(z) b Zeeman interaction c(y)c(y) c(x)c(x) All these molecule, (i) the order of magnitude of Zeeman Splitting is the same. (ii) the J- and K-dependences are the same. ZS ∝ (K c ) 2, ZS ∝ J Magnetic moment is along to c-axis. (out of plane) The magnetic moment comes from the orbital angular momentum of electrons, not from the triplet state!

Rotationally resolved ultrahigh-resolution spectra of jet-cooled dibenzofuran (DF) for the and several vibronic bands up to cm -1 band have been observed. Several thousand lines were assigned and these molecular constants were determined. The S 1 state is assigned to be the 1 A 1 (   *) state. The intensity arises from the vibronic coupling with the S 2 1 B 2 state. The Zeeman broadenings of the rotational lines were also observed, and the J, K-dependence were studied. As a result, the observed Zeeman effects could be explained to be originating from the magnetic moment of the S 1 1 A 1 state induced by mixing with S 2 1 B 2 state by J-L coupling, which suggests that rotationally resolved levels are not mixed with a triplet state largely. Summary Thank you for your attention !

band +443 cm -1 band A type ΔK a = 0, ±2, ・・・ ΔK c = ±1, ±3, ・・・ B type ΔK a = ±1,±3, ・・・ ΔK c = ±1, ±3, ・・・ C type ΔK a = ±1, ±3, ・・・ ΔK c = 0, ±2, ・・・ J c KcKc a b KaKa ΔJ = － 1, 0, 1 Calculated spectrum of band

S 1 ←S 0 and S 2 ←S 0 spectrum of dibenzofuran in a molecular beam (resolution : 0.2 cm -1 ) S 1 ←S 0 S 2 ←S 0

Ultrahigh-resolution spectrum of cm -1 band (P lines)

Doppler-free absorption spectoroscopy of iodine molecule Chopper PBS: Polarization Beam splitter I 2 Cell PBS Laser Photo -diode Photo -diode CW single-mode dye laser Single mode UV laser beam Doubling cavity