Simulated results of position dependence of the transverse temperature (a) and the longitudinal temperature (b) of the guided packet in the filter with different radii <em>R</em> of curvature

<p><strong>Figure 9.</strong> Simulated results of position dependence of the transverse temperature (a) and the longitudinal temperature (b) of the guided packet in the filter with different radii <em>R</em> of curvature. The right insets show a close-up of the transverse temperature in the relevant region (a), or an overview of the longitudinal temperature for the case of <em>R</em> = 50 mm (b).</p> <p><strong>Abstract</strong></p> <p>We propose a scheme of a surface electrostatic velocity filter capable of preparing cold polar molecules on the surface of a substrate by selecting a low-velocity component of an effusive beam from a thermal gas reservoir. Using ND₃ as a molecular sample, the dependence of the performance of the filter on the parameters of both the filter setup and the incident molecular beam is investigated by using a theoretical model and Monte Carlo simulations. A detailed study of the guiding process of molecules, including the evolution of phase space density of the packet in the filter, is carried out and shows that the beam selection process is mainly completed in the front part of the filter.</p

Simulated transverse velocity distribution of the ND₃ molecular beam before (solid curve) and after the bend filter (dots)

<p><strong>Figure 3.</strong> Simulated transverse velocity distribution of the ND₃ molecular beam before (solid curve) and after the bend filter (dots). Compared to the initial beam, the velocity spread of the resulted beam is remarkably reduced from 40 m s⁻¹ (corresponding to a temperature of ~700 mK in the moving frame) to ~13 m s⁻¹ (~75 mK). The dashed line is a fitted one with the formula 1/(\sqrt \pi \alpha )\exp ( - v_{x,y}^2 /\alpha ^2 ). An initial molecular number of <em>N</em> ~ 10⁶ is used for the simulation.</p> <p><strong>Abstract</strong></p> <p>We propose a scheme of a surface electrostatic velocity filter capable of preparing cold polar molecules on the surface of a substrate by selecting a low-velocity component of an effusive beam from a thermal gas reservoir. Using ND₃ as a molecular sample, the dependence of the performance of the filter on the parameters of both the filter setup and the incident molecular beam is investigated by using a theoretical model and Monte Carlo simulations. A detailed study of the guiding process of molecules, including the evolution of phase space density of the packet in the filter, is carried out and shows that the beam selection process is mainly completed in the front part of the filter.</p

Test parameters of the filter

<p><b>Table 1.</b> Test parameters of the filter.</p> <p><strong>Abstract</strong></p> <p>We propose a scheme of a surface electrostatic velocity filter capable of preparing cold polar molecules on the surface of a substrate by selecting a low-velocity component of an effusive beam from a thermal gas reservoir. Using ND₃ as a molecular sample, the dependence of the performance of the filter on the parameters of both the filter setup and the incident molecular beam is investigated by using a theoretical model and Monte Carlo simulations. A detailed study of the guiding process of molecules, including the evolution of phase space density of the packet in the filter, is carried out and shows that the beam selection process is mainly completed in the front part of the filter.</p

Simple schematic of transformation of the two coordinates

<p><strong>Figure 2.</strong> Simple schematic of transformation of the two coordinates. In the new system of coordinate the <em>z</em>' axis is following the bent filter. <em>R</em> is the curvature radius of the electrode. Azimuthal angle is used to indicate the central position of the guided molecular packet in the filter.</p> <p><strong>Abstract</strong></p> <p>We propose a scheme of a surface electrostatic velocity filter capable of preparing cold polar molecules on the surface of a substrate by selecting a low-velocity component of an effusive beam from a thermal gas reservoir. Using ND₃ as a molecular sample, the dependence of the performance of the filter on the parameters of both the filter setup and the incident molecular beam is investigated by using a theoretical model and Monte Carlo simulations. A detailed study of the guiding process of molecules, including the evolution of phase space density of the packet in the filter, is carried out and shows that the beam selection process is mainly completed in the front part of the filter.</p

Dependence of guiding efficiency on the transverse temperature of the incident beam

<p><strong>Figure 5.</strong> Dependence of guiding efficiency on the transverse temperature of the incident beam. The data with an error bar are obtained by 3D Monte Carlo simulations, and the solid curve corresponds to theoretically calculated values.</p> <p><strong>Abstract</strong></p> <p>We propose a scheme of a surface electrostatic velocity filter capable of preparing cold polar molecules on the surface of a substrate by selecting a low-velocity component of an effusive beam from a thermal gas reservoir. Using ND₃ as a molecular sample, the dependence of the performance of the filter on the parameters of both the filter setup and the incident molecular beam is investigated by using a theoretical model and Monte Carlo simulations. A detailed study of the guiding process of molecules, including the evolution of phase space density of the packet in the filter, is carried out and shows that the beam selection process is mainly completed in the front part of the filter.</p

Simulated results of longitudinal central velocity of the bend guided packets as a function of position in the filter for several radii of curvature

<p><strong>Figure 8.</strong> Simulated results of longitudinal central velocity of the bend guided packets as a function of position in the filter for several radii of curvature.</p> <p><strong>Abstract</strong></p> <p>We propose a scheme of a surface electrostatic velocity filter capable of preparing cold polar molecules on the surface of a substrate by selecting a low-velocity component of an effusive beam from a thermal gas reservoir. Using ND₃ as a molecular sample, the dependence of the performance of the filter on the parameters of both the filter setup and the incident molecular beam is investigated by using a theoretical model and Monte Carlo simulations. A detailed study of the guiding process of molecules, including the evolution of phase space density of the packet in the filter, is carried out and shows that the beam selection process is mainly completed in the front part of the filter.</p

Simulated results for position dependence of the relative peak phase space density of the guided ND₃ molecular beam in the filter with <em>R</em> = 150 mm

<p><strong>Figure 11.</strong> Simulated results for position dependence of the relative peak phase space density of the guided ND₃ molecular beam in the filter with <em>R</em> = 150 mm. The phase space density of the guided beam is first enhanced as the packet moves from the position of = 0° to = 10°, and then gradually reduced when the position changes from = 10° to = 70°. All data are normalized to one at the position of = 10°.</p> <p><strong>Abstract</strong></p> <p>We propose a scheme of a surface electrostatic velocity filter capable of preparing cold polar molecules on the surface of a substrate by selecting a low-velocity component of an effusive beam from a thermal gas reservoir. Using ND₃ as a molecular sample, the dependence of the performance of the filter on the parameters of both the filter setup and the incident molecular beam is investigated by using a theoretical model and Monte Carlo simulations. A detailed study of the guiding process of molecules, including the evolution of phase space density of the packet in the filter, is carried out and shows that the beam selection process is mainly completed in the front part of the filter.</p

Simulated longitudinal velocity distribution of the ND₃ molecular beam before (solid curve) and after the bend filter (dots)

<p><strong>Figure 4.</strong> Simulated longitudinal velocity distribution of the ND₃ molecular beam before (solid curve) and after the bend filter (dots). The velocity spread and the most probable velocity of the guided molecular packet are both greatly reduced with respect to the original beam. The final beam has a most probable velocity of 49 m s⁻¹ with a velocity spread of 75 m s⁻¹ after the surface filter. The dashed line is a fitted one with the formula \frac{{2v_z }}{{\alpha ^2 }}\exp ( - v_z^2 /\alpha ^2 ). An initial molecular number of <em>N</em> ~ 10⁶ is used for the simulation.</p> <p><strong>Abstract</strong></p> <p>We propose a scheme of a surface electrostatic velocity filter capable of preparing cold polar molecules on the surface of a substrate by selecting a low-velocity component of an effusive beam from a thermal gas reservoir. Using ND₃ as a molecular sample, the dependence of the performance of the filter on the parameters of both the filter setup and the incident molecular beam is investigated by using a theoretical model and Monte Carlo simulations. A detailed study of the guiding process of molecules, including the evolution of phase space density of the packet in the filter, is carried out and shows that the beam selection process is mainly completed in the front part of the filter.</p

Schematic of the surface electrostatic velocity filter

<p><strong>Figure 1.</strong> Schematic of the surface electrostatic velocity filter. An effusive beam is produced by expansion of a low source pressure gas of polar molecules through a pulsed valve, and then enters into the surface electrostatic velocity filter. Only molecules below a certain threshold velocity can be guided by the filter, while faster ones rush out of the guiding tube. The inset illustrates the two-dimensional (2D) cut through the bend filter in a plane perpendicular to both the electric plates and the substrate, together with contours of a tubular electrostatic field above the surface of the electrode (in units of V/m).</p> <p><strong>Abstract</strong></p> <p>We propose a scheme of a surface electrostatic velocity filter capable of preparing cold polar molecules on the surface of a substrate by selecting a low-velocity component of an effusive beam from a thermal gas reservoir. Using ND₃ as a molecular sample, the dependence of the performance of the filter on the parameters of both the filter setup and the incident molecular beam is investigated by using a theoretical model and Monte Carlo simulations. A detailed study of the guiding process of molecules, including the evolution of phase space density of the packet in the filter, is carried out and shows that the beam selection process is mainly completed in the front part of the filter.</p