Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 8233, MONARIS, F-75005, Paris, France FORMATION OF HYDROXYLAMINE FROM AMMONIA AND HYDROXYL RADICALS Emilie-Laure Zins, Lahouari Krim

The presence of NH 3 in the interstellar medium is very promising in terms of possible exobiologically-relevant reactions. - NH 3 /H 2 ratio in the ISM is compared the H 2 O/H 2 one which is Over 50 molecular species containing nitrogen have been detected in the gas phase towards various astronomical environments. Formation of aminated species in the inter- and circum-stellar medium (ISM and CSM) - Chemical models have tried to reproduce the observed abundances of N-bearing species in the various environments of the ISM with limited success.

Numerous radiation chemical studies of pure NH 3 or NH 3 mixed in water have produced an absorption band at ∼ 1500 cm −1, which has also typically been attributed to NH 4 +.

The mass spectral results during warming of the irradiated ammonia-water ice show that new chemical species such as H 2, O 2, H 2 O 2, NH 2 OH and (NH 2 ) 2 were released into the gas phase between 130 and 200K.

Experiments carried out at 3K to control the reaction and the mobility of reactants Reactivity in neon matrix : useful to elucidate the reaction pathways Reactivity in solid and gaz phases Helium or neon Solid phase or gas phase Cryogenic mirror T= 3K Ne He H2OH2O reactants Solid sample VUV light The irradiation of the sample can be carried out either during the condensation of the gaseous species or after the condensation Deuterium Lamp: NH 3

Surface Irradiation of an ammonia ice: formation of NH 2 radicals. Before irradiation After irradiation

VUV-co-irradiation NH 3 / Ne : NH 3 Concentration effects and ab initio and DFT calculations Theoretical determination of the IR spectra associated to the (NH 2 )(NH 3 ) n complexes, 0  n  3, and comparison with the experimental data

What are the effects of the replacement of 50% of NH 3 by H 2 O in the co- irradiated neon matrix? Influence of water molecules on the NH 3 photolysis reaction

OH-NH 3 OH-NH 2 Not observed NH 2 OH Observed Radicalar complexes: NH 2 -NH 3, NH 2 -H 2 O and OH-H 2 O

OH and NH 3 co-injection NH 3 IR OH ° NH 3 Cryogenic mirror (3 K – 10 K) IR Reactivity of ground state OH radical with NH 3 OH bombardment of and NH 3 ice

Formation and Isolation of ground state OH radical Cold plasma: Microwave discharge Cryogenic mirror T= 3K Helium or neon Solid phase or gas phase Discharged H 2 O H 2 O ice

H 2 O + NH 3 / Ne OH + NH 3 / Ne NH 2

NH 3 Concentration effects A threshold amount of NH 2 seems necessary to form NH 2 OH NH 3 NH 2 NH 2 OH OH (HNO, NO…) OH

(1) NH 3 + OHNH 2 + H 2 O  H = -50 kJ/mol Ea = 10 kJ/mol (2) NH 2 + OH NH 2 OH Ea = 0 kJ/mol  H = -250 kJ/mol (1) Ennis et al J. Am. Chem. Soc. 2009, 131, 1358 (2) Wang et al J. Phys. Chem. A. 2004, 108, (3) Klippenstein et al J. Phys. Chem. A. 2009, 113, (4) Fedossev et al J. Chem. Phys and Congiu et al Astro. J. Lett (3) NH 2 OHNH 2 O + H 2 O HNO + H 2 ONO + H 2 O + OH (4) NOHNOH 2 NO / HNOHNH 2 OH H H-atom addition reactions Step not identified

Cheng et al ChemPhyschem E(kJ/mol) H 2 NO t-HNOH c-HNOH NOH 2 was not observed t-HNOH radical generated on VUV irradiation of NO in solid hydrogen with IR absorption lines at 1242, 1064 and 726 cm -1. Isomers of H 2 NO

(3) Klippenstein et al J. Phys. Chem. A. 2009, 113, (3) NH 2 OHNH 2 O + H 2 O HNO + H 2 ONO + H 2 O + OH and observed at 1323 cm -1 NO predicted at 1340 cm -1

Annealing: warmup-recool cycles NH 2 OH NO