[Collisional energy transfer for K(6S)+H2-->K(4D)+H2]

Area of Science:

• Atomic and Molecular Physics
• Quantum Optics
• Chemical Physics

Context:

• Potassium (K) atoms were excited to the 6S or 4D states using two-photon absorption with an OPO laser.
• Experiments were conducted in a temperature-controlled cell at 413 K with varying H2 pressures (4-40 Pa).
• Collisions between excited K atoms (K(6S, 4D)-K) were negligible under experimental conditions.

Purpose:

• To measure the cross sections for the deactivation of excited potassium atoms in the 6S and 4D states by collisions with molecular hydrogen (H2).
• To determine the radiation lifetimes of the K(6S) and K(4D) states.
• To investigate the energy transfer pathways from the K(6S) state, particularly the transition to the K(4D) state.

Summary:

• Time-resolved fluorescence was monitored to determine effective lifetimes and deactivation cross sections.
• The population dynamics revealed that H2 collisions enhance the population of the K(4D) state originating from the K(6S) state.
• Radiation lifetimes were determined to be (97 ± 15) ns for 6S and (300 ± 45) ns for 4D.
• Total deactivation cross sections by H2 collisions were (1.6 ± 0.3) x 10⁻¹⁴ cm² for 6S and (40 ± 6) x 10⁻¹⁴ cm² for 4D.
• A cross section of (1.4 ± 0.3) x 10⁻¹⁴ cm² was obtained for the 6S → 4D transition.

Impact:

• The study quantifies the collisional deactivation rates of excited potassium atoms by H2, providing crucial data for atomic physics research.
• It highlights physical quenching to the 4D state as the dominant energy depletion channel from the 6S state.
• Findings contribute to understanding energy transfer mechanisms in atomic collisions and inform theoretical models.