# A Small Fullerene (C24) may be the Carrier of the 11.2 micron Unidentified Infrared Band

## TL;DR

This study proposes that a small fullerene (C24) molecule is the carrier of the 11.2 micron unidentified infrared band in space, supported by spectral analysis and theoretical calculations, suggesting a non-polar, spheroidal molecular origin.

## Contribution

The paper introduces a novel identification of C24 as the carrier of the 11.2 μm UIR band, combining spectral deconvolution, molecular modeling, and DFT calculations.

## Key findings

- C24 fits the intrinsic spectral profile of the UIR band
- Spectroscopic parameters of C24 are consistent across different objects
- C24's spectral energy distribution matches observed UIR features

## Abstract

We analyze the 11.2 {\mu}m unidentified infrared band (UIR) spectrum from NGC 7027 and identify a small fullerene (C24) as a plausible carrier. The blurring effects of lifetime and vibrational anharmonicity broadening obscure the narrower, intrinsic spectral profiles of the UIR band carriers. We use a spectral deconvolution algorithm to remove the blurring, in order to retrieve the intrinsic profile of the UIR band. The shape of the intrinsic profile, a sharp blue peak and an extended red tail, suggests that the UIR band originates from a molecular vibration-rotation band with a blue band head. The fractional area of the band-head feature indicates a spheroidal molecule, implying a non-polar molecule and precluding rotational emission. Its rotational temperature should be well approximated by that measured for non-polar molecular hydrogen, ~825 K for NGC 7027. Using this temperature, and the inferred spherical symmetry, we perform a spectral fit to the intrinsic profile that results in a rotational constant implying C24 as the carrier. We show that the spectroscopic parameters derived for NGC 7027 are consistent with the 11.2 {\mu}m UIR bands observed for other objects. We present density functional theory (DFT) calculations for the frequencies and infrared intensities of C24. The DFT results are used to predict a spectral energy distribution (SED) originating from absorption of a 5 eV photon, and characterized by an effective vibrational temperature of 930 K. The C24 SED is consistent with the entire UIR spectrum and is the dominant contributor to the 11.2 and 12.7 {\mu}m bands.

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Source: https://tomesphere.com/paper/1701.07911