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