Overview: CHNO isomers - Centro de Astrobiología

Investigation of HNCO isomers in icemantles: an experimental approachBarbara Michela GiulianoCentro de Astrobiología (CSIC/INTA)

Overview: CHNO isomersLab. spectroscopiccharacterization:gas-phase from MW to FIR[Brünken et al. 2009 and refstherein]solid-state (matrix isolation)[Teles et al. 1989, Chem. Ber.122, 753 and refs therein]From: Brünken et al. 2009, ApJ, 697, 880.

Overview: CHNO isomersPhotochemistry (VUV):gas-phase photodissociation:H+NCO; HN+CO[Okabe 1970, J. Chem. Phys. 53, 3507]matrix isolation isomerization:isocyanic (HNCO) ⇆ cyanic (HOCN)[Milligan & Jacox 1964, J. Chem. Phys. 40, 2457]

Overview: CHNO isomersAstronomy:simplest species which contain the four most importantbiogenic elementsHNCO first detected in the SgrB2 (Snyder & Buhl 1972)and later in many sourcesHOCN tentatively identified in SgrB2 (Brünken et al.2009) and four more sources (Marcelino et al. 2010)HCON recently detected in B1, L1544, L193, L1527(Marcelino et al. 2009)No identification of HNCO on the interstellar grains(contrary to its anion OCN − )

Overview: CHNO isomersHNCO formation?in the gas phasegas-grain chemistryReaction pathways leading to HNCOisomerization? To explain the presence of higher-lying isomers in hotcores and other warm regions.

Overview: CHNO isomersTheule et al. [2011, A&A 530, A96] investigated the HOCNformation from the thermal reaction of HNCO:H 2 O icesFeature of HOCN at ca. 1230 cm -1 is absent.

ExperimentsInvestigation of HNCO formation and possible isomerizationin IS ice analogues by means of vacuum UV irradiation andthermal desorption of different ice mixtures generated in theISAC set-up (UHV chamber) using FTIR spectroscopy andmass spectrometry.UHV chamberMW H 2 -discharge lampICEWINDOW: 8KQuadrupoleMS

Previous experiments:H 2 O:NH 3 :COGrim & Greenberg 1987, ApJ 321, L91 (OCN − );van Broekhuizen et al. 2004, A&A 415, 425 (HNCO).No UHV chamber →Water contamination

H 2 O:NH 3 :COExperiments have been carried out in ISAC on few ML: theHNCO feature (ca. 2260 cm -1 ) is absent.Experiments on thicker ices with simultaneous deposition andirradition:no efficient production of the HNCO species

H 2 O:HCNGerakines et al. [2004, Icarus 170, 202] observed HNCO andOCN - as products of irradiation and photolysis.Our results for the IR spectra are in agreement with the previousstudies.HNCOOCN −Isomerization???

H 2 O:HCNExperiments on thicker ices: FTIR spectroscopySmall feature which is characteristic of the HOCN isomerHNCOHOCN Vibration Frequency Relative Intensityν CN2286.3 1.00δ COH1221.9 0.92Matrix isolation data, from Teles et al. (1989) Chem. Ber. 122,

H 2 O:HCNData from mass spectrometry:43: Molecular ion(not specific)17: HO fragmentfrom HOCN isomer?Few MLThicker ice

Conclusions and future perspectiveThe formation of the HNCO species in ices mixture ofastrophysical interest has been observedThe efficiency of the process is quite lowIt is very difficult to detect the presence of othertautomeric speciesInvestigation ”in situ” of the gas-solid interface bymeans of laser absorption techniques?

AcknowledgementsPeople:Antonio Jiménez-EscobarGuillermo M. Muñoz CaroJosé CernicharoFunding:Scientific committeefor selecting mycontributionThe audience for thekind attention!CONSOLIDER-INGENIO(ASTROMOL)CSD2009‐00038Place:Centro de Astrobiología(CSIC/INTA)