Knowledge Bank

Prior to this investigation, the spectroscopic information on $HI+$ molecular ion was limited to that obtained from low resolution work using photoelectron techniques. A vibration-rotation study has now been carried out of the $X2\Pi \Omega$ electronic state of $Hl+$ in an a.c. glow discharge using a diode laser spectrometer with velocity modulation. A total of more than 100 transitions belonging to the $(\nu \prime \leftarrow \nu \prime \prime )=(1\leftarrow 0)$ and $(2\leftarrow 1)$ vibrational bands of the $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 3/2$ spin substate and to the $(1\leftarrow 0)$ vibrational band of the $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 1/2$ spin substate have been recorded in the frequency range from $1990cm-1$ to $2260cm-1$ for J up to 15.5. At an estimated rotational temperature of the discharge of about 700K, the observed full width at half maximum was $0.004cm-1$. Large hyperfine splittings arising from magnetic dipole and electric quadurpole interactions have been observed for low J transitions belonging to both of the $\Pi$ substates. Precise values of hyperfine and fine structure constants as well as the vibrational and rotational constants were obtained. Preliminary values for the most important constants are listed below. Vibration-rotation constants: \begin{eqnarray*} \begin{array}{llll} \omega_{e} = 2195.2425(19)cm^{-1},& B_{e} = 6.33077(69) cm^{-1},& P_{e} = 3.5202(40) cm^{-1},& q_{e} = -0.0038(10) cm^{-1}\ \omega_{e} x_{e} = 39.5970(10) cm^{-1}, & \alpha_{B} = 0.17540(43)cm^{-1}, &\alpha_{p} = 0.0498(23) cm^{-1} \end{array} \end{eqnarray*} Hyperfine coupling constants: \begin{eqnarray*} \begin{array}{ll} a + \frac{1}{2} (b+c) = 0.05112(7) cm^{-1},& d = 0.09945(51) cm^{-1}\ 1 - \frac{1}{2} (b+c) = 0.0983(96)cm^{-1},& \epsilon Q_{qo} = -.02377(57) cm^{-1} \end{array} \end{eqnarray*} Details of the experiment and the fitted molecular parameters will be presented.