Discovery of Interstellar Silicon Monoxide

Wilson, R. W.; Penzias, A. A.; Jefferts, K. B.; Kutner, Marc L.; Thaddeus, P.

doi:10.1086/180769

Cited by 185 publications

(205 citation statements)

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“…Silicon monoxide, SiO, was discovered in space from observation of rotational lines in its ground vibrational state in 1971 [2], but much stronger lines from excited vibrational states were observed accidently three years later [3], and soon shown to be the result of population inversion and maser amplification [10]. SiO masers are now among the best studied and understood astronomical masers [11], and SiO is unique among astronomical diatomic molecules: vibrationally excited maser emission in CO, CS, and SiS has been the subject of extensive, but unsuccessful searches.…”

Section: Siomentioning

confidence: 99%

“…There is very little experimental or theoretical information on partially hydrogenated silicon molecules such as H 2 Figure 4. Postulated silicon molecules that are good candidates for laboratory and astronomical detection.…”

Section: Laboratory and Astronomical Discovery Of Newmentioning

confidence: 99%

“…The radio astronomical observations of SiO in space in the early 1970s [2] and the discovery of its remarkable maser emission in vibrationally excited states [3][4][5] provided an important impetus to the laboratory rotational spectroscopy of silicon molecules. Nevertheless the laboratory work proceeded slowly in the succeeding twenty years, owing to the difficulty of producing these highly refractory molecules in the gas phase in adequate concentrations.…”

Section: Introductionmentioning

confidence: 99%

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Silicon molecules in space and in the laboratory

2003

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Despite the highly non-volatile nature of Si, silicon bearing molecules are a significant trace constituent of the gas associated with late-type stars and star forming regions, representing nearly 10% of the molecular species that have been identified in space. The early astronomical detection of SiO and its remarkable maser emission stimulated laboratory studies of other small silicon species that were crucial to the astronomical identifications. Although the pace of this laboratory work until recently has been slow, the application of Fourier transform microwave spectroscopy to supersonic molecular beams has overcome many experimental difficulties, yielding the detection of more than 20 new silicon chains and rings of astronomical interest during the past three years. Three of these, the rhomboidal ring SiC 3 and the isovalent linear molecules SiCN and SiNC, have now been found in space, and with dedicated searches other recently discovered silicon molecules may soon be found. A number of exotic silicon molecules of astronomical and chemical interest should be amenable to laboratory detection with present techniques.

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Section: Siomentioning

confidence: 99%

Section: Laboratory and Astronomical Discovery Of Newmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Silicon molecules in space and in the laboratory

2003

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“…The silicon monoxide (SiO) molecule was detected for the first time in the interstellar medium by Wilson et al (1971) through the J = 3 → 2 radio line emission from the galactic source Sagittarius B2, shortly after the first detection of the interstellar CO molecule (Wilson et al 1970). Since then, SiO has been detected in a variety of astrophysical objects, and the modelling of observed molecular spectra showed that the SiO molecule, in contrast to CO, is mostly present in regions associated with warm, dense, and shocked gas.…”

Section: Introductionmentioning

confidence: 99%

Rotational excitation of SiO by collisions with helium

Dayou

Balança

2006

A&A

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Context. Within shocked regions of the interstellar medium and circumstellar environment of AGB stars the proper modelling of SiO line emission through non-LTE radiative transfer calculations requires accurate values of collisional rate coefficients. Aims. The present study focuses on the transitions among the rotational levels of the SiO molecule in its ground vibrational state induced by collision with He. The H 2 molecule being the main colliding partner for the astrophysical regions of interest, the collisional process between SiO and para-H 2 ( j = 0) is also investigated in an approximated way. Methods. A new 2D SiO-He potential energy surface is computed by means of highly correlated ab initio calculations. Collisional rate coefficients corresponding to the pure rotational (de)excitation of SiO by collision with He are obtained from close-coupling quantum scattering calculations of inelastic cross sections. The SiO-He potential energy surface is also employed to compute rate coefficients for the rotational (de)excitation of SiO by collision with para-H 2 ( j = 0). Results. Rate coefficients for rotational levels up to j = 26 and kinetic temperatures in the range 10-300 K are obtained for the SiO-He colliding system. The large asymmetry of the SiO-He potential energy surface induces a propensity rule that favours odd ∆ j transitions over even ∆ j. The estimated values of the SiO-para-H 2 ( j = 0) rate coefficients are compared with those of Turner et al. (1992) for the twenty first rotational levels. As a result of significant differences between the SiO-He interaction potentials employed in the two studies, the rate coefficients are found to differ by a factor 2.5-5 for the main rotational transitions, whatever the temperature range.

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“…Since the first identification of the interstellar SiO molecule in thermal and maser emission ( Wilson et al 1971;Snyder & Buhl 1974), it has been a unique tool for studying physical and chemical phenomena in space. Nowadays, the SiO maser emission of three silicon isotopomers, 28 Si 16 O, 29 Si 16 O, and 30 Si 16 O, has been detected in a large number of late-type stars and Orion KL; 28 Si 16 O thermal emission has also been widely detected in hot regions of molecular clouds and in outflow regions ( Martín-Pintado et al 1992), as well as in late-type stars.…”

Section: Introductionmentioning

confidence: 99%