1. PI Total time #CoIs, team Yuri Beletsky 28h (ELT 42m) 5 Co-Is (both observers and theoreticians) Interstellar chemistry with ELT Observing Diffuse Interstellar Bands (DIB) in a variety of environments (the Galaxy and LMC) we can constrain the nature of DIB carriers. Using extremely high-resolution spectroscopy we plan to compare DIB profiles with laboratory spectra (gas-phase) of the molecules.

2. Scientific rationale DIBS: The origin of diffuse interstellar bands (DIBs) remains unknown since their discovery in 1922. Well over 250 such bands have been found (UV + V) so far. Possibly related to complex carbonaceous gas-phase molecules (fullerenes, polycyclic aromatic hydrocarbons (PAH), carbon chains)

3. Immediate objectives Obtain extremely both high-resolution (R > 100000) and high signal-to-noise spectra (SNR > 1000) of selected targets in LMC Compare very high resolution DIB profiles with laboratory spectra (gas- phase!) of the molecules Shapes of DIB profiles may be specific to some carriers which can allow an identification based on a careful investigation of a single feature only. Challenge: 12 m star: SNR~1000, R~100000 VLT ~ 700 hELT ~ 28 h (6h AO) UHRF R~600000

4. RunTargetR.A.Dec.ToTMagNotes ADIB carrier5h-69˚28h12S/N > 10 3 ELT Justification: Given the required R > 100000 and SNR > 1000 such a project is enormously time consuming for available ground-based telescopes. Legacy Value: Extremely high-resolution stellar spectra can be also used for precise chemical composition analysis, etc. Data Reduction: The data reduction is straightforward. RunMPModeAOT.FOVPixel Notes A1 R=100000 None285’50.5 µmB band