Tentative identification of urea and formamide in ISO-SWS infrared spectra of interstellar ices

Abstract

Abstract. Laboratory experiments involving vacuum ultraviolet (VUV) irradiation of solid isocyanic acid (HNCO) at 10 K, followed by infrared spectroscopy (FTIR), are used to interpret the complex spectra associated with Interstellar Medium (ISM) dust grains, particularly the spectra associated with the icy phase observed toward dense molecular clouds. The comparison of the infrared spectra of the photolysis products with spectra recorded from the protostellar source NGC 7538 IRS9 shows that the "unexplained" 1700 cm −1 feature can be attributed to the contribution of several species H 2 CO (formaldehyde), HCONH 2 (formamide) and H 2 NCONH 2 (urea) mixed with H 2 O as the main contributor. Urea, formaldehyde and NH− (ammonium cyanate) may also contribute to a band at 1470 cm −1 , widely observed in many protostellar infrared sources and which remains up to now poorly explained in numerous ISO-SWS spectra. Isocyanic acid could be a precursor of formamide and urea in interstellar ices.

Shedding light on the formation of the pre-biotic molecule formamide with ASAI

“…However, this route resulted in an overabundance of NH2CHO and an underabundance HNCO, since the latter was efficiently hydrogenated to yield formamide, the final product. Raunier et al (2004) performed experimental Vacuum Ultra Violet (VUV) irradiation of solid HNCO at 10 K, which led to NH2CHO among the final products. They proposed that photodissociation of HNCO yields free H atoms that subsequently hydrogenate other HNCO molecules in the solid to finally give NH2CHO.…”

Infrared spectrum of formamide in the solid phase

“…Formamide was first detected (in 1971) in the gas phase in Sgr B2 and later in the long period comet C/1995 O1 Hale- Bopp (2000) and in the young stellar object W33A (1999), and recently (2004) there has been a tentative report of ice bound formamide in ISO-SWS spectra of the protostellar source NGC 7538 IRS9 [3][4][5][6].…”

“…Laboratory experiments of astrophysical relevance carried out at very low temperatures have investigated (i) the formation of formamide during irradiation of ice mixtures containing H 2 O, NH 3 , CO 2 , CO, HCN, CH 3 OH and HNCO [7][8][9][10][11][12] and (ii) the products from solid formamide dissociation [13] under charged particle irradiation. The Raman and infrared spectral properties of formamide have been reported [14,15] but to date there has been no extensive temperature dependent study of the IR spectra of solid formamide.…”

UCAMMs

“…Raunier et al (2004) proposed a tentative identification of urea in the infrared absorption spectrum of ice mantles of interstellar grains near the protostellar source NGC 7538 IRS9. After the war, he moved to academic life where he dedicated to develop cosmochemistry and isotope geology.…”