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The use of optical cavities in cold molecule trapping, laser cooling and acetylene spectroscopy

Nauta, J (2014) The use of optical cavities in cold molecule trapping, laser cooling and acetylene spectroscopy. Master's Thesis / Essay, Physics.

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The use of optical cavities as an experimental tool is investigated in three different projects within the field of molecular physics. Acetylene is a widely studied molecule to learn about molecular structure, dynamics and interactions. In the physical chemistry group in Helsinki, measurements of higher overtones are carried out to reach a previously unexplored part of the acetylene spectrum. In the first part of this thesis, a new double photon excitation method was implemented by first pumping the molecules to a metastable vibrational stretching state and subsequently performing cavity ring-down spectroscopy. The new method was proven to work and the overtone transition $0010^{0}0^{0}$ $rightarrow$ $2010^{0}0^{0}$ was measured at 6392.403$pm$0.003 cm$^{-1}$. The cold molecules group in Groningen aims to measure parity violation by using ultra-cold molecules as a sensitive probe. In the second part of this thesis, a new dipole trap for SrF molecules is investigated, in which parity violation measurements can be performed. Trap parameters were calculated: an enhancement cavity can provide 4 kW total trapping power at 1064 nm, leading to an optical lattice with a 200 $mu$m waist and a depth of 4 mK for SrF. An experimental design was made based on two separated beams, one for stabilizing the cavity using a PDH lock and the other creating the lattice, while intensity stabilized by an AOM feedback loop. In a literature study methods for improved loading of the dipole trap were investigated, leading to a new single photon transition scheme in which molecules accumulate in dipole trapped high field seeking states. The first part of the designed setup was built and the enhancement cavity, with a measured FSR of 1300 and incoupling efficiency of 80%, was successfully stabilized by a PDH lock. A transfer cavity lock and control system was built to lock a cooling laser for SrF to a HeNe laser. The long term stability of the lock was measured to be 2.9 MHz/30 min for a 663.3 nm diode laser.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Physics
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 08:01
Last Modified: 15 Feb 2018 08:01

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