Neutral barium in solid neon: Optical spectroscopy and first excited state lifetime

Area of Science:

• Atomic Physics
• Spectroscopy
• Cryogenics

Background:

• Matrix isolation spectroscopy allows probing atomic properties in controlled cryogenic environments.
• Previous studies investigated barium atoms in noble gas hosts, but neon matrices present unique challenges and opportunities.

Purpose of the Study:

• To spectroscopically investigate neutral barium atoms in a neon cryogenic crystal at 6.8 K.
• To determine matrix-induced energy level shifts, inhomogeneous linewidths, and lifetimes of barium atoms.
• To understand radiative pathways and relaxation channels affecting barium energy levels in neon.

Main Methods:

• Matrix isolation spectroscopy at 6.8 K.
• Excitation using 10-ns laser pulses at 355 nm to observe fluorescence cascades.
• Tunable continuous-wave laser spectroscopy (700-900 nm) for energy level shifts, linewidths, and lifetime measurements.

Main Results:

• Observed visible and near-infrared emission spectra of barium in neon.
• Determined matrix-induced shifts and inhomogeneous linewidths of barium transitions.
• Measured the lifetime of the barium 5d6s 3D1 state as 0.39 ± 0.02 s, with a predicted increase at lower temperatures.

Conclusions:

• Confirmed multiple radiative pathways and matrix-induced relaxation channels in barium's 5d6s and 6s6p manifolds.
• The study provides essential data for future electron electric dipole moment searches using barium monofluoride in neon matrices.
• Neutral barium atoms in neon matrices are identified as potential sources of background and systematic limitations in sensitive experiments.