Accurate rotational constants for linear interstellar carbon chains: achieving experimental accuracy

Abstract

Linear carbon chain molecular species remain the dominant theme in interstellar chemistry. Their continuous astronomical observation depends on the availability of accurate spectroscopic parameters. Accurate rotational constants are reported for hundreds of molecular species of astrophysical, spectroscopy and chemical interests from the different linear carbon chains; $\mathrm{C}_{{n}}\mathrm{H}$, $\mathrm{C}_{{n}}\mathrm{H}^{-}$, $\mathrm{C}_{{n}}\mathrm{N}$, $\mathrm{C}_{{n}}\mathrm{N}^{-}$, $\mathrm{C}_{{n}}\mathrm{O}$, $\mathrm{C}_{{n}}\mathrm{S}$, $\mathrm{HC}_{{n}}\mathrm{S}$, $\mathrm{C}_{{n}}\mathrm{Si}$, $\mathrm{CH}_{3}(\mathrm{CC})_{{n}}\mathrm{H}$, $\mathrm{HC}_{{n}}\mathrm{N}$, $\mathrm{DC}_{2{n}+1}\mathrm{N}$, $\mathrm{HC}_{2{n}}\mathrm{NC}$, and $\mathrm{CH}_{3}(\mathrm{C}\equiv\mathrm{C})_{{n}}\mathrm{CN}$ using three to four moments of inertia calculated from the experimental rotational constants coupled with those obtained from the optimized geometries at the Hartree Fock level. The calculated rotational constants are obtained from the corrected moments of inertia at the Hartfree Fock geometries. The calculated rotational constants show accuracy of few kHz below irrespective of the chain length and terminating groups. The obtained accuracy of few kHz places these rotational constants as excellent tools for both astronomical and laboratory detection of these molecular species of astrophysical interest. From the numerous unidentified lines from different astronomical surveys, transitions corresponding to known and new linear carbon chains could be found using these rotational constants. The astrophysical, spectroscopic and chemical implications of these results are discussed.

Appendix A: Tables

Table A1 Experimental rotational constants and moments of inertia for HC_2n NC linear carbon chains

Table A2 Calculated parameters for HC_2n NC linear carbon chains

Table A3 Equilibrium rotational constants for HC_2n NC linear carbon chains obtained from $\mathrm{HF}/6\mbox{-}311{+}{+}\mathrm{G}^{**}$

Table A4 Experimental rotational constants and moments of inertia for CH₃(C≡C) _n CN linear carbon chains

Table A5 Calculated parameters for CH₃(C≡C) _n CN linear carbon chains

Table A6 Equilibrium rotational constants for CH₃(C≡C) _n CN linear carbon chains obtained from $\mathrm{HF}/6\mbox{-}311{+}{+}\mathrm{G}^{**}$

Table A7 Experimental rotational constants and moments of inertia for $\mathrm{C}_{n}\mathrm{O}$ linear carbon chains

Table A8 Calculated parameters for $\mathrm{C}_{n}\mathrm{O}$ linear carbon chains

Table A9 Equilibrium rotational constants for $\mathrm{C}_{n}\mathrm{O}$ linear carbon chains obtained from $\mathrm{HF}/6\mbox{-}311{+}{+}\mathrm{G}^{**}$

Table A10 Experimental rotational constants and moments of inertia for $\mathrm{C}_{n}\mathrm{S}$ linear carbon chains

Table A11 Calculated parameters for $\mathrm{C}_{n}\mathrm{S}$ linear carbon chains

Table A12 Equilibrium rotational constants for $\mathrm{C}_{n}\mathrm{S}$ linear carbon chains obtained from $\mathrm{HF}/6\mbox{-}311{+}{+}\mathrm{G}^{**}$

Table A13 Experimental rotational constants and moments of inertia for $\mathrm{HC}_{{n}}\mathrm{S}$ linear carbon chains

Table A14 Calculated parameters for HC _n S linear carbon chains

Table A15 Equilibrium rotational constants for $\mathrm{HC}_{n}\mathrm{S}$ linear carbon chains obtained from $\mathrm{HF}/6\mbox{-}311{+}{+}\mathrm{G}^{**}$

Table A16 Experimental rotational constants and moments of inertia for C_2n H⁻ linear carbon chains

Table A17 Calculated parameters for C_2n H⁻ linear carbon chains

Table A18 Equilibrium rotational constants for $\mathrm{C}_{n}\mathrm{H}^{-}$ linear carbon chains obtained from $\mathrm{HF}/6\mbox{-}311{+}{+}\mathrm{G}^{**}$

Table A19 Experimental rotational constants and moments of inertia for C_2n − 1N⁻ linear carbon chains

Table A20 Calculated parameters for C_2n − 1N⁻ linear carbon chains

Table A21 Equilibrium rotational constants for $\mathrm{C}_{n}\mathrm{N}^{-}$ linear carbon chains obtained from $\mathrm{HF}/6\mbox{-}311{+}{+}\mathrm{G}^{**}$

Table A22 Experimental rotational constants and moments of inertia for $\mathrm{C}_{n}\mathrm{H}$ linear carbon chains

Table A23 Calculated parameters for $\mathrm{C}_{n}\mathrm{H}$ linear carbon chains

Table A24 Equilibrium rotational constants for $\mathrm{C}_{n}\mathrm{H}$ linear carbon chains obtained from $\mathrm{HF}/6\mbox{-}311{+}{+}\mathrm{G}^{**}$

Table A25 Experimental rotational constants and moments of inertia for $\mathrm{C}_{n}\mathrm{N}$ linear carbon chains

Table A26 Calculated parameters for $\mathrm{C}_{n}\mathrm{N}$ linear carbon chains

Table A27 Equilibrium rotational constants for $\mathrm{C}_{n}\mathrm{N}$ linear carbon chains obtained from $\mathrm{HF}/6\mbox{-}311{+}{+}\mathrm{G}^{**}$

Table A28 Experimental rotational constants and moments of inertia for C _n Si linear carbon chains

Table A29 Calculated parameters for C _n Si linear carbon chains

Table A30 Equilibrium rotational constants for C _n Si linear carbon chains obtained from $\mathrm{HF}/6\mbox{-}311{+}{+}\mathrm{G}^{**}$

Table A31 Experimental rotational constants and moments of inertia for CH₃(CC) _n H linear carbon chains

Table A32 Calculated parameters for CH₃(CC) _n H linear carbon chains

Table A33 Equilibrium rotational constants for CH₃(CC) _n H linear carbon chains obtained from $\mathrm{HF}/6\mbox{-}311{+}{+}\mathrm{G}^{**}$