The electronic spectrum of silicon methylidyne (SiCH), a molecule with a silicon–carbon triple bond in the excited state

Abstract

Articles you may be interested inThe electronic spectrum of the fluoroborane free radical. II. Analysis of laser-induced fluorescence and single vibronic level emission spectraThe electronic spectrum of the fluoroborane free radical. I. Theoretical calculation of the vibronic energy levels of the ground and first excited electronic statesThe laser-induced fluorescence spectrum, Renner-Teller effect, and molecular quantum beats in the à 2 Π i -X̃ 2 Π i transition of the jet-cooled HCCSe free radical Investigation of the pure rotational spectrum of magnesium monobromide by Fourier transform microwave spectroscopyThe à 2 ⌺ ϩ -X 2 ⌸ i transition of jet-cooled silicon methylidyne, SiCH, has been recorded by laser-induced fluorescence in the 850-600 nm region. The radical was produced in an electric discharge using tetramethylsilane as the precursor. Fifteen cold bands of SiCH and 16 bands of SiCD have been assigned vibrationally, giving the upper state frequencies as v 2 Јϭ715/558 cm Ϫ1 and v 3 Јϭ1168/1127 cm Ϫ1 for SiCH/SiCD. Rotational analysis of the 0 0 0 and 3 0 3 bands for each isotopomer has given the following molecular structures: r 0 Љ͑Si-C͒ϭ1.692 52͑8͒, r 0 Љ͑C-H͒ϭ1.0677͑4͒, r 0 Ј͑Si-C͒ϭ1.6118͑1͒, and r 0 Ј͑C-H͒ϭ1.0625͑5͒ Å. The silicon-carbon bond length in the X 2 ⌸ ground state of SiCH ͑electron configuration ... 2 3 ͒ is typical for a SiϭC double bond; in the à 2 ⌺ ϩ excited state (... 1 4 ) it corresponds to a triple bond. This work provides the first experimental measurement of the length of the carbon-silicon triple bond.

Near-infrared diode laser spectroscopy of the HCSi radical

“…It is seen that the constants for theX 2 P i ð0 0 0Þ state in the present study are rather close to those obtained from the analysis of the emission spectrum by Cireasa et al [1,3], where a spin-rotation interaction constant c was used (the constant c was undetermined in the present fit). It is seen in Table 1 that the difference of the rotational constant B for thẽ X 2 P i ð0 0 0Þ state between the present value and that obtained by Smith et al [2] is somewhat large corresponding to 15r quoted from Smith et al [2]. The reason for this discrepancy is unknown in the present stage.…”

“…The least squares fit with 20 adjustable constants and equal weights for all the energy differences resulted in a standard deviation of 0.0040 cm À1 , which is almost comparable to the experimental uncertainty expected for such combination differences. The molecular constants thus determined are shown in Table 1, where those obtained in previous investigations by other researchers [1][2][3][4] are given for comparison. It is seen that the constants for theX 2 P i ð0 0 0Þ state in the present study are rather close to those obtained from the analysis of the emission spectrum by Cireasa et al [1,3], where a spin-rotation interaction constant c was used (the constant c was undetermined in the present fit).…”

“…495.00698(30) 508.03(38) c g K 10.31154(16) 10.76(16) c a Numbers in parentheses denote one standard deviation (1r) except for that they are 3r for the constants quoted from Smith et al [2], and they apply to the last digits of the constants. b Dimensionless constants.…”

“…On the other hand, the HCSi radical is a very fascinating molecular species from the spectroscopic viewpoint because it shows a Renner-Teller effect in the ground electronic state. Recently, several spectroscopic investigations [1][2][3][4][5][6] were published, including studies on rotationally resolved spectra associated with the groundX 2 Pð0 0 0Þ state and theà 2 R þ excited states [1][2][3], a study of the vibrational energies related to the Renner-Teller effect in theX 2 P state [4], a study of the hyperfine structure and Stark effect in theX 2 P andà 2 R þ states [5], and an ab initio study characterizing the Renner-Teller effect [6]. The present investigation was carried out to obtain detailed information on the Renner-Teller interaction by studying the rotational energy levels in theX 2 Pð0 1 0Þ state, which have not been previously investigated.…”

Optimal cloud use of quartic force fields: The first purely commercial cloud computing based study for rovibrational analysis of SiCH−

“…[16][17][18][19][20][21] Differently, the SiCH radical is 2 P in its ground state, but it still has a small dipole moment. [22] However, the collisional dynamics and atomic silicon bonding preferences [23][24][25][26] of SiCH are likely to retain the additional electron in much the same way that another known interstellar anion, CN 2 , is believed to form collisionally in the ISM. [27][28][29] Hence, the detection or even nondetection of SiCH 2 in the ISM will provide more details about how anions may form in these environments.…”