Alternating gradient focusing and deceleration of polar molecules

Abstract

Beams of polar molecules can be focused using an array of electrostatic lenses in alternating gradient (AG) configuration. They can also be accelerated or decelerated by applying an appropriate high voltage switching sequence to the lenses. AG focusing is applicable to molecules in both lowfield and high-field-seeking states and is particularly well suited to the problem of decelerating heavy molecules and those in their ground rotational state. We describe the principles of AG deceleration and set out criteria to be followed in decelerator design, construction and operation. We calculate the longitudinal and transverse focusing properties of a decelerator, and exemplify this by 2D-imaging studies of a decelerated beam of metastable CO molecules.

CMIstark: Python package for the Stark-effect calculation and symmetry classification of linear, symmetric and asymmetric top wavefunctions in dc electric fields

“…It is extremely useful in further simulations on the manipulation of polar molecules with inhomogeneous electric fields, where the force exerted on the molecule is directly proportional to µ eff [24].…”

Improved spatial separation of neutral molecules

“…8,10,27,47 We express the shape of the deflector by an equipotential line of a two-dimensional multipole expansion of the electric potential, 8,27,48 with r = x 2 + y 2 and θ = tan −1 (y/x); r 0 and Φ 0 are scaling factors of the geometric size and the potential values, respectively. To obtain deflection in the x direction, either a n or b n can be set to zero, which results in a so-called "a-type" or "b-type" deflector according to the non-zero coefficients, respectively.…”

“…[18][19][20][21] Alternatively, eigenstates of small polar neutral molecules can be separated using switched electric or magnetic fields. 12,[22][23][24][25][26][27][28] Large molecular ions were separated according to their shape using ion-mobility techniques. 29,30 Furthermore, laser fields have been used to deflect and decelerate neutral molecules, [31][32][33][34] which also works for non-polar molecules.…”

Optimizing the resolution of the alternating-gradientm/μselector

“…The application of AG focusing to neutral polar molecules was first proposed by Auerbach, Bromberg, and Wharton [13] and experimentally demonstrated by Kakati and Lainé for ammonia molecules in hfs states [14]. More recently, AG focusing was applied to the deceleration of polar molecules [15][16][17][18], to the guiding of cold molecules from an effusive source [19], and to the guiding of a supersonic jet of CaF molecules [20]. Furthermore, an m/µ selector for neutral molecules, based on the AG principle, was implemented for the conformer separation of neutral molecules [21].…”