We report the observation of the hitherto undetected v = 8 ← v = 0 vibrational overtone in trapped HD + molecular ions, sympathetically cooled by laser-cooled Be + ions. The overtone is excited using 782 nm laser radiation, after which HD + ions in v = 8 are photodissociated by the 313 nm laser used for Be + cooling. The concomitant loss of HD + is detected by the method of secular excitation (Roth et al. in Phys. Rev. A. 74:040501(R), 2006). We furthermore present details of the experimental setup, and we show that results from spectroscopy of v = 8 ← v = 0 overtones in combination with accurate ab initio calculations may yield a new value for the proton-electron mass ratio with an accuracy of order 1 ppb.

We report the detection of eight vibronic bands of C 3 , seven of which have been hitherto unobserved in astrophysical objects, in the translucent cloud towards HD 169454. Four of these bands are also found towards two additional objects: HD 73882 and HD 154368. Very high signal-to-noise ratio (∼1000 and higher) and high resolving power (R = 80, 000) UVES-VLT spectra (Paranal, Chile) allow for detecting novel spectral features of C 3 , even revealing weak perturbed features in the strongest bands. The work presented here provides the most complete spectroscopic survey of the so far largest carbon chain detected in translucent interstellar clouds. High-quality laboratory spectra of C 3 are measured using cavity ring-down absorption spectroscopy in a supersonically expanding hydrocarbon plasma, to support the analysis of the identified bands towards HD 169454. A column density of N(C 3 ) = (6.6 ± 0.2) × 10 12 cm −2 is inferred and the excitation of the molecule exhibits two temperature components; T exc = 22 ± 1 K for the low-J states and T exc = 187 ± 25 K for the high-J tail. The rotational excitation of C 3 is reasonably well explained by models involving a mechanism including inelastic collisions, formation and destruction of the molecule, and radiative pumping in the far-infrared. These models yield gas kinetic temperatures comparable to those found for T exc . The assignment of spectral features in the UV-blue range 3793-4054Å may be of relevance for future studies aiming at unravelling spectra to identify interstellar molecules associated with the diffuse interstellar bands (DIBs). cent clouds, transparent for optical wavelengths. Among them are homonuclear species, such as H2, C2 and C3, which are not accessible to radio observations. Bare carbon chains do not exhibit pure rotational transitions, because of the lack of a permanent dipole moment, and thus only their electronic or vibrational spectral features can be observed. The latter cover the spectral range from the vacuum UV until the far infrared. Determination of the abundances of simple carbon molecules in interstellar clouds is important, as they are considered building blocks for many already known interstellar molecules with a carbon skeleton. c 2012 RAS

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2014 Les sections efficaces différentielles absolues de la diffusion 9Be + p ont été mesurées à 2 ~ Ep 3,8 MeV. Cinq courbes d'excitation à des angles 65° ~ 03B8cm ~ 160° et cinq distributions angulaires à Ep = 2,31; 2,44; 2,56; 2,62 et 2,73 MeV et pour des angles 40° ~ 03B8cm ~ 140° ont été obtenues. L'analyse simultanée de ces résultats et de données existant à Ep ~ 5 MeV a été effectuée dans le formalisme de la matrice R. L'ensemble des données a été ajusté de façon satisfaisante en tenant compte, dans cette gamme d'énergie, de neuf niveaux du 10B situés respectivement aux énergies d'excitation