Knowledge Bank

The vibrational predissociation spectrum of HF dimer at low $(8cm-1)$ $resolution,1$ indicated the vibrational frequency of the hydrogen-bonded HF was approximately $3720cm-1$. In the high (1 MHz) gas-cell absorption $spectrum2$ of $(HF)2$, a band centered at $3868.079cm-1$ was determined to be due to the hydrogen-bonded HF. We have reinvestigated the $3720cm-1$ at higher $(0.7cm-1)$ resolution and have confirmed that it is due to HF dimer. To resolve the two disparate results, an ab initio potential energy surface for HF dimer has been determined using a triple-zeta + polarization basis set, including configuration interaction at the approximate double substituted coupled cluster (ACCD) level. The results from the potential surface and experiments will be discussed.