RESUMO
The Ã(2)Σ(+)-XÌ(2)Πi band system of l-SiC3H in the region 14,700-16,300 cm(-1) was re-investigated by laser induced fluorescence (LIF) and fluorescence depletion spectroscopy. Rotational analyses were made for three intense bands 0(0)(0), 4(0)(1), and 6(0)(1)7(0)(1) by observing high-resolution LIF excitation spectra. The determined rotational constants demonstrate that SiC3H is linear in the à state, as is the case in the XÌ state, and the observed band types are consistent with the vibrational assignments. The ν3(â³) (C1-C2 stretch) level was identified in a newly observed dispersed fluorescence spectrum from the zero-vibrational level of the à state.
RESUMO
Two silicon-bearing carbon chain radicals, SiC2N and SiC3N, were detected in the laboratory by Fourier transform microwave spectroscopy. Molecular constants including the hyperfine coupling constants have been determined for the two radicals in the ground electronic states. The SiC2N and SiC3N radicals have linear structures in the (2)Π ground electronic states with inverted and regular fine structures, respectively, as are the cases for their isoelectronic radicals, SiC3H and SiC4H, indicating that the SiC(n)N radicals have similar electronic structures to the SiC(n +1)H radicals. The electronic structures of SiC2N and SiC3N in the ground states are discussed on the basis of the experimentally determined molecular constants.
RESUMO
Pure rotational spectra of the allenyloxy radical (CH2=CCHO) were observed by Fourier transform microwave (FTMW) and FTMW-millimeter wave double-resonance spectroscopy. Molecular constants including the hyperfine interaction constants of CH2=CCHO in the (2)A(â³) ground electronic state were precisely determined. Ab initio calculations indicate that CH2=CCHO has a linear C-C-C backbone with Cs symmetry, where the formyl group is in the Cs plane and perpendicular to the methylene group. The determined rotational constants and the inertial defect agree well with those derived from the calculations, implying that the calculated molecular structure is reasonable. The fine and hyperfine constants also agree with those derived from the calculated spin density, where the unpaired electron is located mainly on the central carbon atom. The ground state CH2=CCHO can, thus, be described as taking the formylvinyl (CH2=C-CH=O) form rather than as the allenyloxy (CH2=C=CH-È®) form.
RESUMO
We report directional far-infrared emission from the υ = 0 vibrational levels of the 9sσ, 10sσ, 11sσ, 9f, and 10f Rydberg states of NO in the gas phase. The emission around 28 and 19 µm from the 9f state was identified as the downward 9f â 8g and subsequent 8g â 7f cascade transitions, respectively. The emission around 38 and 40 µm from the 10f state was identified as the 10f â 9g and 10f â 9dσπ transition, respectively. Following the excitation of the 9sσ, 10sσ, and 11sσ states, the emission around 40, 60, and 83 µm was assigned as the 9sσ â 8pσ, 10sσ â 9pσ, and 11sσ â 10pσ transitions, respectively. In addition to these emission systems originated from the laser-prepared levels, we found the emission bands from the 8f, 9f, and 10f states which are located energetically above the 9sσ, 10sσ, and 11sσ states, respectively. This observation suggests that the upward 8f â 9sσ, 9f â 10sσ, and 10f â 11sσ optical excitation occurs. Since the energy differences between nf and (n + 1)sσ states correspond to the wavelength longer than 100 µm, the absorption of blackbody radiation is supposed to be essential for these upward transitions.
