### Abstract

Ab initio calculations with the 6-311 G** basis set and all single and double excitations in the CI treatment have been carried out to determine the structure of the HCC radical. The theoretical geometry of R(CC) = 1-209, r(CH) = 1-067 Å (or 1-205 and 1-063, respectively, if corrected for residual errors) is in excellent accordance with the experimental rotational constant. The calculated harmonic vibrational frequencies are v_{1}3450, v_{2} — 540 and v_{3} ~2040 cm^{-1}. An extremely low energy around 2000 cm_{-1} is obtained for the first electronic transition A 3∏ ←X^{2}Σ. Results for the excited state are also given. The theoretical vibrational frequencies, with all possible errors taken into account, are inconsistent with the accepted interpretations of the few experimental results. It is shown, however, that a complete reinterpretation of the spectroscopic observations is possible, by which the present calculations fit with the recent gas phase infrared laser spectroscopic data but remain in definite contradiction with the infrared matrix results.

Original language | English |
---|---|

Pages (from-to) | 139-151 |

Number of pages | 13 |

Journal | Molecular Physics |

Volume | 50 |

Issue number | 1 |

DOIs | |

Publication status | Published - 1983 |

### Fingerprint

### ASJC Scopus subject areas

- Biophysics
- Molecular Biology
- Physical and Theoretical Chemistry
- Condensed Matter Physics

### Cite this

*Molecular Physics*,

*50*(1), 139-151. https://doi.org/10.1080/00268978300102231

**Theoretical equilibrium geometry, vibrational frequencies and the first electronic transition energy of HCC.** / Fogarasi, G.; Boggs, James E.; Pulay, Péter.

Research output: Contribution to journal › Article

*Molecular Physics*, vol. 50, no. 1, pp. 139-151. https://doi.org/10.1080/00268978300102231

}

TY - JOUR

T1 - Theoretical equilibrium geometry, vibrational frequencies and the first electronic transition energy of HCC

AU - Fogarasi, G.

AU - Boggs, James E.

AU - Pulay, Péter

PY - 1983

Y1 - 1983

N2 - Ab initio calculations with the 6-311 G** basis set and all single and double excitations in the CI treatment have been carried out to determine the structure of the HCC radical. The theoretical geometry of R(CC) = 1-209, r(CH) = 1-067 Å (or 1-205 and 1-063, respectively, if corrected for residual errors) is in excellent accordance with the experimental rotational constant. The calculated harmonic vibrational frequencies are v13450, v2 — 540 and v3 ~2040 cm-1. An extremely low energy around 2000 cm-1 is obtained for the first electronic transition A 3∏ ←X2Σ. Results for the excited state are also given. The theoretical vibrational frequencies, with all possible errors taken into account, are inconsistent with the accepted interpretations of the few experimental results. It is shown, however, that a complete reinterpretation of the spectroscopic observations is possible, by which the present calculations fit with the recent gas phase infrared laser spectroscopic data but remain in definite contradiction with the infrared matrix results.

AB - Ab initio calculations with the 6-311 G** basis set and all single and double excitations in the CI treatment have been carried out to determine the structure of the HCC radical. The theoretical geometry of R(CC) = 1-209, r(CH) = 1-067 Å (or 1-205 and 1-063, respectively, if corrected for residual errors) is in excellent accordance with the experimental rotational constant. The calculated harmonic vibrational frequencies are v13450, v2 — 540 and v3 ~2040 cm-1. An extremely low energy around 2000 cm-1 is obtained for the first electronic transition A 3∏ ←X2Σ. Results for the excited state are also given. The theoretical vibrational frequencies, with all possible errors taken into account, are inconsistent with the accepted interpretations of the few experimental results. It is shown, however, that a complete reinterpretation of the spectroscopic observations is possible, by which the present calculations fit with the recent gas phase infrared laser spectroscopic data but remain in definite contradiction with the infrared matrix results.

UR - http://www.scopus.com/inward/record.url?scp=0000145104&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0000145104&partnerID=8YFLogxK

U2 - 10.1080/00268978300102231

DO - 10.1080/00268978300102231

M3 - Article

AN - SCOPUS:0000145104

VL - 50

SP - 139

EP - 151

JO - Molecular Physics

JF - Molecular Physics

SN - 0026-8976

IS - 1

ER -