High Resolution Measurements and Electronic Structure Calculations of a Diazanaphthalene:

[1,6]-naphthyridine.

Sébastien Gruet, Manuel Goubet, Olivier Pirali

ISMS 2014

17/06/2014

2

Astrophysical Background

Naphthalene

Structure of small PAHs molecules

[1,6] Naphthyridine

Complementarity of MW and IR data

• Principal sources of rotational informations (GS)– Microwave spectroscopy – UV for centrosymmetric molecules • Y. Semba et al. J. Chem. Phys. 131, 024303 (2009)

• Publications of high resolution IR data are scarce• S. Albert et al. Faraday Discuss. 150, 71-99 (2011)• B. E. Brumfield et al. J. Phys. Chem. Lett. 3, 1985-1988 (2012)• O. Pirali et al. PCCP, 15, 10141-10150 (2013)

Rotational resolved data in the Literature

HypothesisA. Leger, J. L. Puget, A&A 1984, 137, L5.

Peeters et al, 2002, A&A,390, 1089

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Mid- & Near Infrared (Classical Sources)

(372)30001000

(62)500

(12)100

(1.2)10 600030 250 750

Far-Infrared The AILES Beamline

(Synchrotron Radiation)

Fundamental vibrational modes of PAHs

(meV)cm-1

Room temperature long pathlength cell

Optical pathlength : 150 mSpectral range : 30 – 1000 cm-1

Resolution : 0.00102 cm-1

≈ 30 MHzSpherical moving mirror

MW Radiation

Gas injection

L-shaped antenna Vacuum : ≈ 10-6 mbar

Step by step motor

Stainless steel cell

Spherical mirror(Aluminum)

Pumping group

Pulsed nozzle

Gaussian beam profileW0= 42 mm à 12 GHz

1200 mm

Supersonic Jet

Set-up of the FT-MW spectrometer

Spectral range : 4 – 20 GHz≈ 0.13 – 0.67 cm-1

Resolution : 1.8 kHz ≈ 6.10-8 cm-1

MicroWaveThe PhLAM Laboratory

(Electronic sources)

Pure Rotational Transitions of PAHs

0 1(0.06)

0.5

Experimental Devices

4

Pure Rotational SpectrumPhLAM Laboratory

Ro-vibrational SpectrumAILES Beamline

Experimental Spectra (MW&IR)

5

c

b

Infared transitionsOut of plane vibrational modes

Quantum numbers :

+ hyperfine structure

ca

b

μa = 1.55 Dμb = 0.46 D

Microwave transitions

Spectroscopy of this Asymmetric Top Molecule

a-type b-type

+ hyperfine structure

c-type

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• Two nitrogen atoms () Nuclear-quadrupole hyperfine structure

• Coaxial arrangement of the jet and the Fabry-Perot cavity. Doppler doublets

• 280 transitions assigned and

Collaboration with M. Goubet from the PhLAM laboratory at Lille

Spherical moving mirror

MW Radiation

Gas injection

L-shaped antenna Vacuum : ≈ 10-6 mbar

Step by step motor

Stainless steel cell

Spherical mirror(Aluminum)

Pumping group

Pulsed nozzle

Gaussian beam profileW0= 42 mm à 12 GHz

1200 mm

Supersonic Jet

Analysis of the MW data

7

• 4011 transitions ( 2780 for 38 and 1231 for 34) 38 : and 34 : and

• Use of the LWW software. Graphical search of transitions and quick assignment

• A few transitions still unassigned. Hot bands sequences

[1,6] Naphthyridine

Analysis of the IR data

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[1,6]-naphthyridine

Par. GS (Combined fit: MW + IR data)

ν38 ν34

Band CenterMHz/cm-1 14490562.34(45)

/483.353132(15)25247267.84(47)/842.158205(16)

A 3227.104274(70) 3226.28045(68) 3225.90185(54)B 1276.297178(30) 1276.1874(40) 1276.09822(73)C 914.802113(21) 915.1597(57) 914.8647(12)

ΔJ.103 0.01973(11) 0.01953(12) 0.01973c

ΔK.103 0.16660(89) 0.16524(96) 0.16660c

ΔJK.103 0.04866(58) 0.04954(66) 0.04866c

δJ.106 5.598(61) 5.598c 5.598c

δK.106 70.4(16) 70.4c 70.4c

χaa(N1) 1.5191(18) χbb(N1) -4.6809(12) χaa(N6) -3.6392(15) χbb(N6) 0.2234(17) N lines 280 2780 2460

MW/IR RMS 0.002665 MHz 0.00020 cm-1 0.00020 cm-1

J” 2-17 15-99 15-83Ka” 0-6 14-61 14-41

Results of the fit

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•Anharmonic DFT calculation at the B97-1/cc-pVTZ//ANO-DZP level

•Accurate calculated rotational parameters

•More details about calculations: M. Goubet, O. Pirali, J. Chem Phys. 140, 044322 (2014)

•Useful tool to begin the GSCD analysis by LWW diagram

[1,6]-naphthyridine

Mode GS 38 34

Parameters Calculated Experimental Deviation Calculated Experimental Deviation Calculated Experimental Deviation

A /MHz 3227.595582 3227.104274 -0.491308 3226.48635 3226.28045 -0.20589 3226.1865558 3225.90185 -0.28470

B /MHz 1274.837448 1276.297178 1.459730 1274.77749 1276.1874 1.40991 1274.747511 1276.09822 1.35070

C /MHz 914.0971837 914.802113 0.704929 914.4269554 915.1597 0.73274 914.1271629 914.8647 0.73753

•Anharmonic DFT calculation at the B97-1/cc-pVTZ//ANO-DZP level

Corrected Calculated

ValuesExperimental Deviation

Corrected Calculated

ValuesExperimental Deviation

3225.99504 3226.28045 0.28541 3225.69525 3225.90185 0.20660

1276.23722 1276.1874 -0.04982 1276.20724 1276.09822 -0.10902

915.13188 915.1597 0.02782 914.83209 914.8647 0.03261

Electronic Calculations as Supporting Tools

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Comparison Sim/Exp of the 34-GS band

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• Combining MW and FT-FIR data:– Excited states of small PAHs and derivatives

FA09 – Roger Adams Lab 116 – 11h01 to 11h16 AM

– Spectroscopy of diamond-like and biphenyl-like molecules

• Important database of rotational information in the IR Simulation at different resolution and at low temperature

FluorenePhenanthrene

Naphthalene Azulene

Pure carbonated PAHs

Quinoline

Isoquinoline

Quinoxaline

[1,6] NaphthyridineQuinazoline

[1,5] Naphthyridine

PANHs (PAHs with nitrogen atoms)

Conclusion & Perspectives