Knowledge Bank

The properties of a supersonic beam of molecules from a nozzle source have been studied in a molecular beam electric resonance spectrometer. From the lineshape and relative intensities of electric dipole radiofrequency transitions, the velocity distribution and rotational energy distribution of the beam can be determined. For an HCN beam from a 3.5 mil diameter nozzle at $300\circ K$, the most probable molecular velocity was twice the thermal velocity, and the beam was nearly monoenergetic, the velocity dispersion corresponding to a temperature of about $1\circ K$. The rotational energy distribution was also found to correspond to a low temperature, about $20\circ K$. By using an $SF6$ diluent, the HCN velocity was halved. Evidence for considerable vibrational relaxation of the $SF6$ was also observed. Using this source we have been able to make beams of $ArXe,XeHCl,(HCl)2$ and a series of HF polymers, at least as large as the pentamer. $XeHCl,(HCl)2$ and $(HF)2$ were deflected by an inhomogeneous electric field and are therefore polar molecules. Microwave and radiofrequency transitions for $(HF)2$ and $(DF)2$ have been observed.