Electronic structure of confined carbyne from joint wavelength-dependent resonant Raman spectroscopy and density functional theory investigations

Carbyne, i.e. an infinitely long linear carbon chain (LCC), has been at the focus of a lot research for quite while, yet its optical, electronic, and vibrational properties have only recently started to become accessible experimentally thanks synthesis inside nanotubes (CNTs). While role host CNT in determining optical gap LCCs studied previously, little is known about excited states such ultralong LCCs. In this work, we employ selectivity wavelength-dependent resonant Raman spectroscopy investigate encapsulated double-walled CNTs. addition gap, resonance profile shows three additional resonances. Corroborated with DFT calculations on up 100 C-atoms, assign these resonances vibronic series different electronic state. Indeed, predict existence two optically allowed separated by energy 0.14-0.22 eV limit infinite chain, agreement experimental results. Furthermore, among states, one highest also characterized largest electron-vibration couplings, which explains corresponding overtones.