Vibrationally exciting molecules trapped on a microchip

Abstract

Polar molecules in selected quantum states can be guided, decelerated and trapped using electric fields created by microstructured electrodes on a chip. Here we demonstrate that transitions between two vibrational quantum states can be induced while the molecules are trapped above the chip. We use CO molecules, prepared in the J = 1 rotational level of the a 3Π1, v = 0 state and induce the transition to either the J = 1 or the J = 2 level in the vibrationally excited a 3Π1, v = 1 state with pulsed, narrowband IR radiation. First, the vibrational excitation is studied using CO molecules in a freely propagating molecular beam, in a well-defined homogeneous electric field. Then, we demonstrate that the IR radiation can be coupled to CO molecules that are trapped less than 50 µm above the chip by guiding molecules in the v = 0 level to the center of the chip where they are pumped to the v = 1 level. The molecules remain trapped and are then guided off the chip and state-selectively detected.