State purity of decelerated molecular beams

Cold, velocity-controlled molecular beams consisting of a single quantum state are a powerful tool for exploring molecular interactions. Here, we explore the state purity and resulting dynamics of a Stark-decelerated beam of ammonia molecules where numerous rotational states are initially populated. Under these circumstances, Stark deceleration is shown to be ineffective at producing a molecular beam consisting of a single quantum state. Therefore, quantum state purity must be carefully considered when using Stark decelerated beams and analogous techniques, particularly in collision experiments where contributions from all quantum states must be addressed.

Highlights► We decelerated a molecular beam of ammonia molecules in several rotational states. ► We measured the rotational state distribution of the molecular beam before and after deceleration. ► We modeled the deceleration process using trajectory simulations. ► We found that the deceleration process is not highly quantum state specific for many circumstances.