Knowledge Bank

The pure rotational spectrum of the AlC$2$ (~{X}$2$A$1$) radical in the range 4 - 60 GHz has been measured using Fourier transform microwave (FTMW) methods. The species was produced using the Discharge Assisted Laser Ablation Source (DALAS) technique in a supersonic jet expansion of aluminum vapor and CH$4$, diluted in argon carrier gas. The N = 1 $\to$ 0 and 2 $\to$ 1 transitions have been measured near 22 and 44 GHz, each exhibiting fine structure and hyperfine splittings, arising from the nuclear spin of aluminum, I($\mathrm{<mrow\; data-mjx-texclass="ORD">27</mrow>}$Al) = 5/2. The higher frequency transition was recorded using a newly constructed U-band FTMW system operating at 40 - 60 GHz. The data have been analyzed with a case (b) asymmetric top Hamiltonian, and rotational, fine structure, and hyperfine constants have been determined. Measurements of the $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$C isotopologues are currently underway to establish a precise structure for AlC$2$.