Rotationally-resolved high-resolution laser spectroscopy of the B 2 E’ – X 2 A 2 ’ transition of 14 NO 3 radical 69th International Symposium on Molecular Champaign-Urbana, Illinois, The United States 2014 / June / 16th MI13 Shunji Kasahara 1, Kohei Tada 1†, Takashi Ishiwata 2, and Eizi Hirota 3 1 Kobe University, Japan; 2 Hiroshima City University, Japan; 3 The Graduate University for Advanced Studies, Japan; † Research Fellow of Japan Society for the Promotion of Science.

Introduction Introduction D 3h Wavenumber / 1000 cm NO 2 + O NO 3 NO + O 2 O2 (b 1Σg+)O2 (b 1Σg+) O2 (a 1Δg)O2 (a 1Δg) O2 (X 3Σg-)O2 (X 3Σg-) B 2 E’ A 2 E’’ X 2A2’X 2A2’ Vibronic Band ~ cm -1 (~ 625 nm) Vibronic Band ~ cm -1 (~ 625 nm) 0-0 band ~ cm -1 (~ 662 nm) 0-0 band ~ cm -1 (~ 662 nm) B - X 遷移 K. Mikhaylichenko et al., J. Chem. Phys., 105, 6807 (1996) reaction coordinate NO 2 + O 3 → NO 3 + O 2 N 2 O 5 ⇄ NO 3 + NO 2 B 2 E’ ： … (4e’) 3 (1e’’) 4 (1a 2 ) 2 ~ cm -1 A 2 E’’ ： … (4e’) 4 (1e’’) 3 (1a 2 ) 2 ~ 7000 cm -1 X 2 A 2 ’ ： … (4e’) 4 (1e’’) 4 (1a 2 ) 1 0 cm nm Absorption spectrum of 14 NO 3 (Visible) J. Chem. Soc. Faraday 1176, 785 (1980).

⑤ LIF and Absorption spectra of 14 NO 3 B-X transition Absorption spectrum of 14 NO 3 (Visible) J. Chem. Soc. Faraday 1176, 785 (1980) Wavenumber / cm -1 N 2 O 5 → NO 3 + NO 2 M. Fukushima et al., 67th Int. Symp. Mol. Spectrosc., TI06 (2012) Resolution ： 0.2 cm NO 3 B 2 E’-X 2 A 2 ’ transition

Wavenumber / cm Wavenumber / cm -1 LIF spectra of 14 NO 3 and 14 NO 2 N 2 O 5 → NO 3 + NO 2 R. E. Smalley et al., J. Chem. Phys., 63, 4977 (1975) Vibronic band band M. Fukushima et al., 67th Int. Symp. Mol. Spectrosc., TI06 (2012) NO 2 Resolution ： 0.2 cm -1 INTENSITY ×5 ? 14 NO 2 A 2 B 2 -X 2 A 1 transition (I max at cm -1 ) 14 NO 3 B 2 E’-X 2 A 2 ’ transition

D Exprimental setup Absolute wavenumber mesurement system (Accuracy : cm -1 ) Etalon Liq. N 2 Pump Pulsed Nozzle Skimmer ( ϕ = 2 mm) Filter N 2 O 5 → NO 3 + NO 2 Slit (2 mm) PBS Molecular Beam (Typical linewidth : cm -1 ) N 2 O 5 + Ar Computer 532 nm around 660 or 625 nm Single mode laser ( Γ = cm -1 ) PD BS : Beam splitter PBS : Polarization beam splitter EOM : Electro-optic modulator PD : Photo diode PMT : Photomultiplier tube BS EOM I 2 Cell Heater 300 ℃ NO 2 + He Ring Dye Laser Nd:YVO 4 Laser Mirror Heater off Photon Counter PMT

 ~ 150 strong (> 15% of max) lines and more than 3000 weak (< 15% of max) lines were observed. ← too many!  The rotational assignment was very difficult. (1) Combination difference → cm -1 line pairs (2) Zeeman effect → Unambiguous Assignment High-resolution LIF spectrum 14 NO 3 B-X 0-0 band at 662 nm 0.1 cm cm -1

σ-pump (H ⊥ E) ΔM J = ±1 π-pump (H // E) ΔM J = cm -1 Zeeman effect around cm G 70 G 100 G 160 G 190 G 220 G 305 G 40 G 70 G 100 G 160 G 190 G 220 G 305 G σ-pump: ΔM J = ±1 π-pump: ΔM J = 0 (σ:4+6/π:2+3) pair

Symmetry-adopted basis sets The X 2 A 2 ’ state: The B 2 E’ state: Hund’s case (b) basis Hund’s case (a) basis

The X 2 A 2 ’ state: H Z = g S μ B H·S The B 2 E’ state: H Z = g S μ B H·S + g L μ B H·L eff Refs: Endo et al., J. Chem. Phys., 81, 122 (1984) Hirota, High-Resolution Spectroscopy of Transient Molecules, Springer (1985) μ B (= ×10 -5 cm -1 G -1 ): Bohr magneton, g S : the electron spin g factor, g L : the electron orbital g factor, and ζ e d: the effective value of. Zeeman Hamiltonians and matrix elements

(σ:4+6/π:2+3) pair Zeeman splitting: transition to ( 2 E’ 3/2, J = 1.5) J = 1.5 ← 1.5 J = 1.5 ← 0.5 At 300 G – 0.5 – 1.5 – – 0.5 – 1.5 MJMJ σ-pump ΔM J = ±1 g S = (4) g S = 2.103(6) g L ζ e d = – 0.138(11) – – 0.5 – – 0.5 – 1.5 MJMJ Magnetic field / G Term energy / cm -1 J’ = 1.5 J” = 0.5 J” = 1.5 ΔMJ (MJ”)ΔMJ (MJ”)

σ-pump (H ⊥ E) ΔM J = ±1 π-pump (H // E) ΔM J = 0 Zeeman effect around cm G 360 G cm G 305 G 190 G cm -1 σ-pump: ΔM J = ±1 π-pump: ΔM J = 0 (σ:2+3/π:1+2) pair

H = 0 G 20 G 40 G 70 G 130 G190 G250 G300 G360 G σ-pump (H ⊥ E) ΔM J =±1 Energy / cm -1 J’’=1.5 J’’=0.5 J’=0.5 MJMJ ‐ ‐ ‐ ‐ 1.5 Magnetic field / Gauss B 2 E’ 1/2 X 2 A 2 ’(K’’=0 ， N’’=1) σ-pump (H ⊥ E) Wavenumber / cm -1 Magnetic field / Gauss 70 Gauss The determined g-factors: lower: g S = (fixed) upper: g S = 1.892(26) g L ζ e d = 0.214(51) (σ:2+3/π:1+2) pair Zeeman splitting: transition to ( 2 E’ 1/2, J = 0.5) σ-pump : ● π-pump : ● Calc : ― M J = ‐ 0.5 M J = +0.5 Perturbation ?

2 E’ 3/2 2 E’ 1/2 2 A 2 ’ (K” = 0, N” = 1) J’ = 1.5 J’ = 0.5 J” = 0.5 J” = cm -1 QR R Q QP 2 E’ 3/2 ← 2 A 2 ’ : 7 transitions Assigned line pairs from the Zeeman splittings σ-pump: ΔM J = ±1 π-pump: ΔM J = 0 σ-pump: ΔM J = ±1 π-pump: ΔM J = 0 2 E’ 1/2 ← 2 A 2 ’ : 15 transitions

Wavenumber / cm Wavenumber / cm -1 N 2 O 5 → NO 3 + NO 2 R. E. Smalley et al., J. Chem. Phys., 63, 4977 (1975) M. Fukushima et al., 67th Int. Symp. Mol. Spectrosc., TI06 (2012) NO 2⑤ Resolution ： 0.2 cm -1 INTENSITY × cm -1 band ： ν 1 LIF spectra of 14 NO 3 and 14 NO 2 How about the vibronic bands?

NO 2 N 2 O 5 → NO 3 + NO 2 High-resolution LIF spectra 14 NO cm -1 band and 14 NO 2 NO 2 R (2) R (0) R (4) P (2) 0.2 cm -1 Resolution ： cm -1

N 2 O 5 → NO 3 + NO 2 NO 2 Small signal, large background → difficult to analyze NO 3 signal Resolution ： cm -1 High-resolution LIF spectra 14 NO cm -1 band and 14 NO 2

Wavenumber / cm Wavenumber / cm -1 NO 2 N 2 O 5 → NO 3 + NO 2 R. E. Smalley et al., J. Chem. Phys., 63, 4977 (1975) cm -1 band ： 2ν 4 M. Fukushima et al., 67th Int. Symp. Mol. Spectrosc., TI06 (2012) Resolution ： 0.2 cm -1 INTENSITY ×5 LIF spectra of 14 NO 3 and 14 NO 2

N 2 O 5 → NO 3 + NO 2 NO cm -1 Resolution ： cm -1 High-resolution LIF spectra 14 NO cm -1 band and 14 NO 2

N 2 O 5 → NO 3 + NO cm -1 High-resolution LIF spectra 14 NO cm -1 band and 14 NO 2 Resolution ： cm -1 Large signal, small background, compared with cm -1 band Large signal, small background, compared with cm -1 band

0 G 12 G 25 G 37 G 50 G 62 G J’ = 1.5 MJMJ J” = π - pump (H // E), ΔM J = 0 Zeeman Splitting at cm -1 line pair J” = cm -1

N 2 O 5 → NO 3 + NO cm -1 R (0.5) Q (1.5) High-resolution LIF spectra 14 NO cm -1 band and 14 NO 2 Resolution ： cm -1 2 E’ 3/2 2 E’ 1/2 X 2 A 2 ’ ( ʋ ”=0, K” = 0, N” = 1) J’ = 1.5 J’ = 0.5 J” = 0.5 J” = cm -1 QR R Q QP

Summary  We have observed high-resolution fluorescence excitation spectra of 14 NO 3 B-X transition. (1) 0-0 band [15070 – cm -1 ] (2) cm -1 band [15872 – cm -1 ] * (3) cm -1 band [16048– cm -1 ] * (* Not full region.)  Rotational assignment is difficult except the transitions from the X 2 A 2 ’ (K” = 0, N” = 1) levels. ( cm -1 pairs)  Unambiguous assignment of these cm -1 pairs is completed from the observed Zeeman splittings.  How about 15 NO 3 ? MI14

Acknowledgement  Prof. Masaru Fukushima (Hiroshima City University) for his LIF spectrum of 15 NO 3.  Ms. Kanon Teramoto and Mr. Tsuyoshi Takashino (Undergraduate students, Kobe University) for their help.  Thank you for your attention!  Prof. Masaaki Baba (Kyoto University) for experimental setup at early stage.  How about 15 NO 3 ? MI14

Electronic states of NO 3 B 2 E’ A 2 E” X 2A2’X 2A2’ ~ cm -1 (~ 662 nm) ~ 7000 cm -1 (~ 1430 nm) E” E’ A2’A2’ A2”A2” LUMO SOMO NO 3 …Planer triangle ⇒ D 3h Radical ⇒ Doublet (Gaussian03, RHF/6-31g)

Vibrational Assignment Vibrational Assignment Wavenumber / cm cm -1 band M. Fukushima et al., 67th Int. Symp. Mol. Spectrosc., TI06 (2012)振動 モー ド 既約 表現 遷移波数 (cm -1 ) X [1] [2] A [3] B ν1ν1 a1’a1’ ν2ν2 a2”a2” ν3ν3 e’1480 (?)1435 ν4ν4 e’380530~ 385 2ν42ν4 ν1ν cm -1 band [1] T. Ishiwata et al., J. Phys. Chem., 87, 1349 (1983) [2] R. R. Friedl et al., J. Phys. Chem., 91, 2721 (1987) [3] T. J. Codd et al., 68th Int. Symp. Mol. Spectrosc., WJ05 (2013) Normal Mode of NO ν 2 A 2 ” ν 1 A 1 ’ ν 3a E’ ν 3b ν 4a E’ ν 4b E’ ν = E’ a 1 ’, a 2 ’, e’ B state Vibrational level Vibronic level band

Complicated structure of the 662 nm band Vib. modeFrequency Anharmonic constant ν 1 (a 1 ’) ν 2 (a 2 ”) ν 3 (e’) ν 4 (e’) – – [Codd et al., 67th OSU meeting, TI01 (2012)] The A state vibrational frequencies in cm -1 X 2A2’X 2A2’ A 2 E” B 2 E’ { – cm -1 region: 10 ~ 15 E’-type levels Complicated structure of the 662 nm band: (mainly) vibronic interaction with dark A state?? 7060 cm -1 E” × A 2 ” = E’ cm -1

B 2 E’ ： Hund’s coupling case(a) J R P S L Λ Σ z(c) x(a)=y(b) KN J R L S z(c) x(a)=y(b) X 2 A 2 ’(v=0) ： Hund’s coupling case(b) good quantum number : Λ, S, Σ, J, P, M J, K good quantum number : N, K, S, J, M J Hund’s Couplig Case Hund’s Couplig Case