Jet-Cooled Spectroscopy of 1-Naphthylmethyl, 2-Naphthylmethyl &

Acenaphthenyl Radicals

Nahid Chalyavi

2

Astrochemical Significance of PAHs

Jenniskens P. et al., Ap.J., 183, 87, 1973

Diffuse Interstellar Bands

Cohen M. et al., A & A, 390, 147, 2002

Red Rectangle Bands

F.C. Gillett et al., Ap.J., 183, 87, 1973

Unidentified Infrared Bands Interstellar Dust Grain Model

Kwok, Nature 430, 985 (2004)

3Kwok, Nature 430, 985 (2004)

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Resonance-Stabilized Radicals (RSRs)

Preferable product from decomposition of

stable species

Slower rate of reaction and dissociation

compared to localized radicals

Can reach high concentration in reaction

environment

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Supersonic Jet Expansion

High pressure gas (Ar)

Vacuum

Pulsed nozzle

cold molecules in centre of beam

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Detector

Source

Extractionof ions

Time-Of-Flight MS

Resonance-Enhanced Multiphoton Ionization (REMPI)

Ionisation continuum

l1

+e-

l2

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Laser-Induced Fluorescence (LIF) & Dispersed Fluorescence (DF) Spectroscopy

Vibrational Coordinate

Ener

gy

DF

Vibrational Coordinate

Ener

gyLIF

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1-Naphthylmethyl Radical LIF vs. REMPI

A' = 1.987 GHz A" = 1.996 GHzB' = 1.102 GHz B" = 1.121 GHzC' = 0.709 GHz C" = 0.718 GHz

Band Type: a/b=1.325Band Origin: 17240.68 cm-1

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Dispersed Fluorescence (DF)

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Comparison with RR and DIB Bands

The Red Rectangle Emission wavelength has been corrected for

the speed of nebulae (18.9 km/sec)

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2-Naphthylmethyl Radical LIF vs. REMPI

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Dispersed Fluorescence (DF)

13

Comparison with RR and DIB Bands

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Acenaphthenyl Radical LIF vs. REMPI

15

Dispersed Fluorescence (DF)

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Comparison with RR and DIB Bands

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Conclusions & Future Work

Jet-cooled spectroscopy of three resonance-stabilized radicals containing

naphthalene moiety has been studied

A coincidence is found between 1-naphthylmethyl radical origin transition and a

red rectangle emission band

The coincidence suggests that some structures similar to these radicals might be

the carriers of red rectangle bands

Consider other resonance-stabilized radicals with similar structures

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AcknowledgementsDr. Timothy SchmidtDr. Rob SharpDr. Masakazu NakajimaThe Laser Spectroscopy Group