Conformer separation of 3-aminophenol using an electrostatic deflector

In chemistry the word conformer describes one of a set of stereoisomers, all having the same molecular formula and identical constitution (connectivities between the atoms) but differing by the spatially orientations of their functional groups in the molecular frame. Often these structural differences between individual conformers are subtle. For 3-aminophenol (C₆H₇NO), hereafter 3AP, only the position of one single hydrogen atom distinguishes the two stable conformers cis- and trans-3AP. In the case of 3AP this modest change gives rise to a significant rise in the permanent dipole moment (trans-3AP 0.77D vs. cis-3AP 2.3D). We show that it is possible to spatially separate and further select the two conformers of 3 AP by passing a molecular beam of 3AP through an electrostatic deflector. Polar molecules experience a force in the inhomogeneous electric field of the deflector given by the negative gradient of the Stark energy. As a result the conformers will be deflected according to their dipole moment, spatially separating the two conformers at the end of the deflector. Using R2PI to selectively ionize either of the two conformers, via the S₁larrS₀ transition, deflection profiles of each conformer was obtained changing the spatial position of the laser focus. These profiles show a strong deflection of cis-3AP, having the largest dipole moment, while the trans-3AP is only modestly deflected. Positioning the laser focus at the deflected region (lens position at 9.7 mm) only cis-3 AP will contribute to the observed signal whereas the opposite will be the case when going to the depleted region of the curve (lens position at 12.0 mm) since all of the cis-3AP is deflected from this part leaving only trans-3AP. Furthermore, we have shown that deflected polar molecules can be efficiently oriented by combined laser and static electric fields. Currently we are investigating applications of the new conformer separation feature combin- ing it with the ability to orient polar molecules.