High-resolution rotational spectroscopy of iminosilylene, HNSi

Abstract

By means of Fourier transform microwave spectroscopy of a supersonic beam, the fundamental rotational transition of isotopic and vibrationally excited iminosilylene, HNSi, has been detected. In addition to seven isotopic species, vibrational satellite transitions from more than 30 vibrationally excited states, including the three fundamental modes, have been detected. Those from ν 2 are particularly intense, enabling detection of transitions from as high as (0,22 0 ,0) (i.e. ∼10,000 cm −1 above ground). At high spectral resolution, well-resolved nitrogen quadrupole structure has been observed in nearly every transition. Excitation of ν 1 or ν 3 changes eQq(N) little, but eQq(N) systematically decreases with increasing excitation of the ν 2 bend, from a value of 0.376(5) MHz for (0,0 0 ,0) to −2.257(5) MHz for (0,20 0 ,0). With the large amount of new data in hand, it has also been possible to determine the leading vibration-rotation constants (α i and γ i ) for ν 2 or ν 3 to high precision, and derive a revised semi-empirical equilibrium structure for this fundamental triatomic molecule. Various electronic and molecular properties of iminosilylene have been calculated at the coupled cluster level of theory, and these generally agree well with experiment and previous calculations. An unsuccessful search for HSiN, a highly polar isomer calculated to lie nearly 3 eV above HNSi, is also reported.

Chemical equilibrium in AGB atmospheres: successes, failures, and prospects for small molecules, clusters, and condensates

“…Yes (Drouin et al 2010) Si 3 C ∼ 1 × 10 −7 S, C stars ∼ 0.1 (Stanton et al 2005) No Si 5 C ∼ 3 × 10 −6 S, C stars 0.27 B3LYP/cc-pVTZ e No SiNH ∼ 1 × 10 −8 S, C stars 0.34 Yes (Bogey et al 1991;McCarthy et al 2015) SiF ∼ 1 × 10 −10 S, C stars 1.126 (Karna & Grein 1987) Yes (Tanimoto et al 1983) SiCl ∼ 1 × 10 −9 S, C stars 1.53 (Gosavi & Strausz 1986) Yes (Tanimoto et al 1984)…”

“…See CDMS c . PH ∼ 1 × −10 M, S, C stars 0.396 (CDMS) c Yes (Goto & Saito 1993;Klisch et al 1998 C stars 0.34 (McCarthy et al 2015) Yes (Bogey et al 1991;McCarthy et al 2015) SiF ∼ 1 × −10 S, C stars 1.126 (Karna & Grein 1987) Yes (Tanimoto et al 1983) SiCl ∼ 1 × −9 S, C stars 1.53 (Gosavi & Strausz 1986) Yes (Tanimoto et al 1984) PS ∼ 1 × −7 M stars 0.565 (Müller & Woon 2013) Yes (Ohishi et al 1988 ∼ 1 × −9 M stars 2.78 (Dewar et al 1988) No BF ∼ 1 × −9 S, C stars 0.50 (Dewar et al 1988) No AlH ∼ 1 × −8 S, C stars 0.30 (Matos et al 1988) Yes (Halfen & Ziurys 2004)…”

“…Thermochemical data for this species are taken from the Chemkin Thermodynamic Database (Kee et al 2000), which assigns a formation enthalpy at 298.15 K of 160.6 kJ mol −1 based on quantum calculations. An astronomical search is feasible because the rotational spectrum has been measured in the laboratory (McCarthy et al 2015), although the calculated dipole moment is low (0.34 D; McCarthy et al 2015). The silicon monohalides SiF and SiCl are also potentially detectable in AGB atmospheres.…”

High-temperature rotation–vibration spectrum of iminosilylene (HNSi)

“…Chen et al 11 investigated the formation of HNSi using matrix-isolation FTIR spectroscopy and assigned the absorptions at 3570.8, 514.9 and 1196.9 cm −1 to HNSi. Recently, McCarthy et al 12 detected the fundamental rotational transition J = 0–1 of HNSi using Fourier transform microwave spectroscopy. They also determined the υ 1 , υ 2 and υ 3 bands of HNSi at 3588, 523 and 1198 cm −1 , respectively.…”

“…Lind et al 23 performed the characterization of the ground state of the HNSi–HSiN system using CCSD, CCSD(T), CASSCF and internally contracted multireference configuration interaction (ICMRCI) methods. McCarthy et al 12 determined the molecular structures at the CCSD(T) level of theory using Dunning's hierarchies of correlation consistent polarized valence and polarized core–valence basis sets. Their calculated values compared well with their experimental ones.…”