1. High-resolution Laser Spectroscopy
ISMS, Univ. of Illinois, June 2015
High-resolution Laser Spectroscopy
of the S1←S0 Transition of Cl-naphthalenes
Shunji Kasahara, Ryo Yamamoto, and Kenichiro Kanzawa
Molecular Photoscience Research Center, Kobe University, Japan
Naphthalene
2-Cl naphthalene
(2-ClN)
1-Cl naphthalene
(1-ClN)

2. Rotationally Resolved High-Resolution Laser Spectroscopy
Introduction
PAHs (Polycyclic Aromatic Hydrocarbons)
benzene
naphthalene
anthracene
H. Katô, M. Baba, and S. Kasahara, Bull. Chem. Soc. Jpn. 80, 456 (2007)
M. Baba et. al.,
J. Chem. Phys. 130, (2009)
D. Y. Beak et. al., Bull. Chem. Soc. Jpn. 79(1), 75 (2006), etc.
K. Yoshida et. al.,
J. Chem. Phys. 130, (2009), etc.
Rotationally Resolved High-Resolution Laser Spectroscopy
Molecular Constants 　　Molecular Structure
Linewidth
Energy Shift Excited-State Dynamics
Zeeman Effect　　　

3. Molecular Constants Molecular Structure
Introduction
Intramolecular
heavy-atom effect ? S0 IC
IVR
ISC
absorption
fluorescence
phosphorescence S1 S2 T1
2-Chloronaphthalene
(2-ClN)
1-Chloronaphthalene
(1-ClN)
Molecular Constants 　　Molecular Structure
Linewidth
Energy Shift Excited-State Dynamics
Zeeman Effect　　　

4. Experimental set up

5. Observed high-resolution spectrum
Marker Etalon
cm-1
Doppler-free Saturation Spectrum of I2
cm-1
cm-1
cm-1
Sub-Doppler Fluorescence Excitation Spectrum of 2-ClN

6. 2-Cl naphthalene (2-ClN)

7. Low-resolution spectrum （Vibronic bands）
Dispersed Fluorescence Spectrum
LIF spectrum
(a)
(a)
(b)
(c)
(d)
(b)
(c)
(d)
Jacobson et al., J. Chem. Phys. 87, 269 (1987)．

8. High-resolution fluorescence excitation spectrum of 0-0 band of 2-ClN S1←S0 transition
band origin
cm-1
Calculated spectrum
(35Cl only, a-type 18 %, b-type 82 %,
Tr = 20 K, line width 15 MHz)
Observed spectrum

9. Molecular constants of 2-35Cl naphthalene
S0 (ref )
S1 (ref)
υ =0
A/ cm-1
(37)
(36)
(3)
(1) B
(24)
(24)
(1)
(13) C
(19)
(20)
(1)
(2) ∆J
2.25(86) ×10-10
　2.29(86)×10-10
1.668(17)×10-10 ∆K
2.356(76)×10-9
　2.132(67)×10-8
9.23(27)×10-9
a-type 18%
∆JK
3.34(45)×10-9
　3.16(45)×10-9
1.33(30)×10-10
b-type 82% δJ
2.62(41)×10-10
　2.80(42)×10-10
3.502(67)×10-11 δK
-1.37(44)×10-8
-1.43(44)×10-8　
6.7(10)×10-10
origin/cm-1
(2)
(1)
Std.dev.
fitted lines
4583
assigned lines
4725
822 a b
(ref) D. F. Plusquellic, et al. J. Chem. Phys, 115, 225 (2001)

10. High-resolution fluorescence excitation spectrum of 0-0 band of 2-ClN S1←S0 transition
band origin
cm-1
Calculated spectrum
(35Cl only, a-type 18 %, b-type 82 %,
Tr = 20 K, line width 15 MHz)
Observed spectrum

11. High-resolution fluorescence excitation spectrum of 0-0 band of 2-ClN S1←S0 transition
pPKa (J)
rPKa(J)
+ :
+ : ∆Kｃ = +1
- : ∆ Kｃ= -1

12. Zeeman effect for the 0-0 band of 2-ClN S1←S0 transition (with magnet)
H = 0 T
H = 1 T
rP0 (28)
rP0 (27)
rP0 (26)
pP5 (8)
pP5 (7)
pP5 (9)
rP0 (29)

13. Zeeman splittings of the 0-0 band of 2-ClN S1←S0 transition
J-L coupling
(electronic Coriolis interaction)
0.5 T
Ka = 0 (J =Kｃ) S2
（ cm-1 band）
J-L coupling term
-2JzLz S1
ZS : Zeeman splitting
C : naphthalene : C = cm-1
2-Cl naphthalene : C = cm-1
Lz : Angular momentum along with z-axis
μB : Bohr magneton J Kc
a(x)
b(y)
c(z)
For the 2-ClN, (i) the order of magnitude of Zeeman Splitting is small.
　　　　 (ii) the J- and K-dependences are found. 　ZS ∝ (Kc)2, ZS ∝ J
　　　These results are almost the same as naphthalene.
Foe benzene and naphthalene,　Bull. Chem. Soc. Jpn. 80, 456 (2007) ，etc.

14. Low-resolution spectrum （Vibronic bands）
Dispersed Fluorescence Spectrum
LIF spectrum
(a)
(a)
(b)
(c)
(d)
(b)
0 – 0 band
τ = 31ns → Γ = 5.1 MHz
(c)
cm-1band
τ = 11 ns → Γ = 14 MHz
(d)
Jacobson et al., J. Chem. Phys. 87, 269 (1987)．

15. High-resolution fluorescence excitation spectrum of 000+1042 cm-1 band of 2-ClN S1←S0 transition
band origin: (1) cm Trot = 30 K a-type:b-type = 1:3
Linewidth (FWHM) 50 MHz
band origin
Calc.
Obs.

16. Molecular constants of 2-35Cl naphthalene
S0 (ref )
S1 (ref)
υ =0
1042 cm-1 band
A/ cm-1
(37)
(36)
(26)
(3)
(1) B
(24)
(24)
(85)
(1)
(13) C
(19)
(20)
(36)
(1)
(2) ∆J
2.25(86) ×10-10
　2.29(86)×10-10
1.668(17)×10-10 ∆K
2.356(76)×10-9
　2.132(67)×10-8
9.23(27)×10-9
a-type 18%
∆JK
3.34(45)×10-9
　3.16(45)×10-9
1.33(30)×10-10
b-type 82% δJ
2.62(41)×10-10
　2.80(42)×10-10
3.502(67)×10-11 δK
-1.37(44)×10-8
-1.43(44)×10-8　
6.7(10)×10-10
origin/cm-1
(2)
(2)
(1)
Std.dev.
fitted lines
4583
1596
assigned lines
4725
1651
822 a b
(ref) D. F. Plusquellic, et al. J. Chem. Phys, 115, 225 (2001)

17. High-resolution fluorescence excitation spectrum of 000+1042 cm-1 band of 2-ClN S1←S0 transition
band origin: (1) cm Trot = 30 K a-type:b-type = 1:3
Linewidth (FWHM) 50 MHz
band origin
Calc.
Obs.

18. High-resolution fluorescence excitation spectrum of 000+1042 cm-1 band of 2-ClN S1←S0 transition
Calc.
Obs.

19. Energy shifts in the 000+1042 cm-1 band of 2-ClN S1←S0 transition

20. High-resolution spectrum of vibronic band of 2-ClN S1←S0 transition×1
Excess Energy
476
1042
1396
Lifetime (ns) 31 23 11 8
Natural
Line width (MHz)
5.1　
6.9　 14 20
0 – 0
×3.5
cm-1
×3.5
cm-1
×3.5
cm-1

21. 1-Cl naphthalene (2-ClN)

22. High-resolution fluorescence excitation spectrum of 0-0 band of 1-Cl naphthalene (1-ClN) S1←S0 transition
S0: A = (30), B = (84), C = (35)　[cm-1]
S1: A = (31), B = (84), C = (35) [cm-1]
band origin (3) cm-1 Trot = 60 K a-type:b-type = 1:2
Linewidth (FWHM) 120 MHz
band origin
Calc.
Obs.
Wavenumber / cm-1

23. High-resolution fluorescence excitation spectrum of 0-0 band of 1-Cl naphthalene (1-ClN) S1←S0 transition
Calc.
Obs.

24. Zeeman effect for the 0-0 band of 1-ClN S1←S0 transition (with magnet)
Zeeman splittings are not found because
(1) Zeeman splittings are small.
(2) the rotational lines are overlapped even if there are J, K-dependence.
What is the background?
H = 1.2 T
H = 0 T
Wavenumber / cm-1

25. Summary
We have observed high-resolution fluorescence excitation spectra and
their Zeeman effect by crossing a UV laser perpendicular to a molecular beam.
2-ClN
1-ClN
Measurement of the 0-0 band
・Rotationally resolved spectra have been
observed and assigned.
(Typical linewidth was 15 MHz)
・Rotational line has not been resolved.
(Typical linewidth was 120 MHz)
・Molecular constants were estimated
from simulation and partial assignment
of the observed spectrum.
Under the external magnetic field up to 1.2 T
・Zeeman effect has been observed.
・Zeeman splittings are small.
・J, K-dependence were found.
・Zeeman effect has not been observed.
*There is strong background signal.
　Measurement of the vibronic bands
・Rotationally resolved spectra have been
observed and assigned.
・Energy shifts were found.
・Not yet.

26. Thank you for your attension !

27. Comparison between 1-ClN and 2-ClN for the 0-0 band of S1←S0 transition (1)
2-ClN 0-0 band: τ = 31 ns *, Γ = 5.1 MHz
band
origin
31416　　　 31417　　　　31418　 　 　 　　31420　 　　31421　　 　31422
1-ClN 0-0 band: τ = 3.4 ns*, Γ = 47 MHz
31571　　 　31572　　　 　 　31574　 　　31575　　　　31576　 　　31577
*Jacobson et al., J. Chem. Phys. 87, 269 (1987).
Wavenumber / cm-1

28. Comparison between 1-ClN and 2-ClN for the 0-0 band of S1←S0 transition (2)
2-ClN 0-0 band: τ = 31 ns *, Γ = 5.1 MHz
　 　　　　 　 　　　 　　　　 　　 　　　
1-ClN 0-0 band: τ = 3.4 ns*, Γ = 47 MHz
　　　　 　　　　 　 　　　 　　 　　　　 　　　
*Jacobson et al., J. Chem. Phys. 87, 269 (1987).
Wavenumber / cm-1