Can neutral and ionized PAHs be carriers of the UV extinction bump and the diffuse interstellar bands?

Up to now, no laboratory-based study has investigated polycyclic aromatic hydrocarbon (PAH) species as potential carriers of both the diffuse interstellar bands (DIBs) and the 2175 A UV bump. We examined the proposed correlation between these two features by applying experimental and theoretical techniques on two specific medium-sized/large PAHs (dibenzorubicene C30H14 and hexabenzocoronene C42H18) in their neutral and cationic states. It was already shown that mixtures of sufficiently large, neutral PAHs can partly or even completely account for the UV bump. We investigated how the absorption bands are altered upon ionization of these molecules by interstellar UV photons. The experimental studies presented here were realized by performing matrix isolation spectroscopy with subsequent far-UV irradiation. The main effects were found to be a broadening of the absorption bands in the UV combined with slight red shifts. The position of the complete pi - pi* absorption structure around 217.5 nm, however, remains more or less unchanged which could explain the observed position invariance of the interstellar bump for different lines of sight. This favors the assignment of this feature to the interstellar PAH population. As far as the DIBs are concerned, neither our investigations nor the laboratory studies carried out by other research groups support a possible connection with this class of molecules. Instead, there are reasonable arguments that neutral and singly ionized cationic PAHs cannot be made responsible for the DIBs.Comment: 11 pages, 7 figures, 1 tabl

Effectiveness of cardiac resynchronization therapy in heart failure patients with valvular heart disease: comparison with patients affected by ischaemic heart disease or dilated cardiomyopathy. The InSync/InSync ICD Italian Registry

AimsTo analyse the effectiveness of cardiac resynchronization therapy (CRT) in patients with valvular heart disease (a subset not specifically investigated in randomized controlled trials) in comparison with ischaemic heart disease or dilated cardiomyopathy patients.Methods and resultsPatients enrolled in a national registry were evaluated during a median follow-up of 16 months after CRT implant. Patients with valvular heart disease treated with CRT (n = 108) in comparison with ischaemic heart disease (n = 737) and dilated cardiomyopathy (n = 635) patients presented: (i) a higher prevalence of chronic atrial fibrillation, with atrioventricular node ablation performed in around half of the cases; (ii) a similar clinical and echocardiographic profile at baseline; (iii) a similar improvement of LVEF and a similar reduction in ventricular volumes at 6-12 months; (iv) a favourable clinical response at 12 months with an improvement of the clinical composite score similar to that occurring in patients with dilated cardiomyopathy and more pronounced than that observed in patients with ischaemic heart disease; (v) a long-term outcome, in term of freedom from death or heart transplantation, similar to patients affected by ischaemic heart disease and basically more severe than that of patients affected by dilated cardiomyopathy.ConclusionIn 'real world' clinical practice, CRT appears to be effective also in patients with valvular heart disease. However, in this group of patients the outcome after CRT does not precisely overlap any of the two other groups of patients, for which much more data are currently available

ASSIGNMENT OF THE LOWEST EXCITED STATES OF C70C_{70} AND EVIDENCE FOR FLUORESCENCE FROM THE SINGLET S2S_{2} STATE

Author Institution: Institut de Physique Exp\'{e}rimenta***e, Universit\'{e} de LausanneHighly structured fluorescence, phosphorescence and fluorescence-excitation spectra of $C_{70}$ in neon matrices are reported. Fluorescence from both $S_{1}$ and $S_{2}$ states is observed and these are identified as being of $A^{\prime}_{2}$ and $E^{\prime}_{1}$ symmetry and have gas phase energies estimated at 15560 and $15725 cm^{-1}$, respectively. A third singlet state is identified in the excitation spectrum and is proposed to be of $A^{\prime \prime}_{2}$ symmetry with an estimated gas phase energy of $16000 cm^{-1}$. Finally, the phosphorescence is dominated by vibrational bands of $e^{\prime}_{1}$ symmetry pointing to a lowest triplet state of $A^{\prime}_{2}$ symmetry. Its energy lies at $12588 cm^{-1}$ above that of the ground state in the neon matrix. From a comparison with data from the literature, the existence of a second triplet state of $E^{\prime}_{1}$ character is inferred, which lies about $165 cm^{-1}$ above the lowest triplet state, i.e. with the same energy separation as the lowest two singlet states

Assignment of the near-UV absorption spectrum of C60

The absorption spectrum of C60 embedded in Ne matrixes in the 410-360 nm region is revisited. A complete assignment of the absorption lines therein is proposed in terms of transition to the ungerade states 1 1G1u, 1 1T1u and 2 1T1u states, with progression of Jahn-Teller hg modes and of the totally sym. ag modes. The authors also identify a new progression at l ? 375 nm, which the authors attribute to the transition to the 2 1T2u state and its hg and gg Jahn-Teller modes. Its pure electronic origin is at .apprx.26700 cm-1. [on SciFinder (R)

Phosphorescence of C60 in rare gas matrixes

The phosphorescence of C60 in Kr and Xe matrixes is reported. It consists of a progression of bands of monotonically decreasing intensity which belong to the hg(1) mode but in Xe weaker contributions from the t1u, t2u, hu and gu modes are also present. In Xe matrixes, the phosphorescence stems from a distribution of sites extending up to 150 cm-1 to the red of the main and most prominent one having its origin at 12714 cm-1. The phosphorescence lifetime is 16 +- 1 ms in Xe and 60 +- 5 ms in Kr. The phosphorescence is attributed to the 3T2g state, whose gas phase energy the authors est. to be 12925 +- 10 cm-1 from the gas-to-matrix shift. [on SciFinder (R)