Water vapor at a translational temperature of $1\mathrm{K}$

We report the creation of a confined slow beam of heavy-water $\left({\mathrm{D}}_2\mathrm{O}\right)$ molecules with a translational temperature around $1\mathrm{K}$. This is achieved by filtering slow ${\mathrm{D}}_2\mathrm{O}$ from a thermal ensemble with inhomogeneous static electric fields exploiting the quadratic Stark shift of ${\mathrm{D}}_2\mathrm{O}$. All previous demonstrations of electric-field manipulation of cold dipolar molecules rely on a predominantly linear Stark shift. Further, on the basis of elementary molecular properties and our filtering technique we argue that our ${\mathrm{D}}_2\mathrm{O}$ beam contains molecules in only a few rovibrational states.

Figure 1

The lowest rotational energies of ${\mathrm{D}}_2\mathrm{O}$ as a function of the applied electric field $E$. The five most abundant states $\mid J,\tau ,M⟩$ in the guided beam are indicated. The Stark shifts are obtained by numerically diagonalizing the Stark Hamiltonian $(J=0,\dots ,12)$, following Ref. 13.

Figure 2

(Color online) Schematic of the experiment. On the left is the effusive source, which injects thermal ${\mathrm{D}}_2\mathrm{O}$ molecules into the four-wire guide. Neighboring electrodes have opposite polarity, creating a quadrupolar electric field. Molecules that are slow enough are guided through the first and second (not shown) $90°$ bends and are finally detected by a mass spectrometer.

Figure 3

Detector signal versus the electrode voltage $V$. The data follow a quartic law in $V$, as illustrated by the $V^4$ fit (solid line). The dotted line shows a $V^2$ fit attempt.

Figure 4

Stark shifts $\mathrm{\Delta }{W}_{\mathrm{S}}$ in an electric field of $100\mathrm{kV}∕\mathrm{cm}$ of LFS rotational states of ${\mathrm{D}}_2\mathrm{O}$ in its vibrational and electronic ground state, as a function of the zero-field rotational energy $E_{\mathrm{rot}}$. The inset shows the Boltzmann factor at $T=300\mathrm{K}$. The five most Stark-shifted states are labeled $\mid J,\tau ,M⟩$. Note that the spin-statistical weighting is not shown.