Abstract ...................................................... iii
Zusammenfassung ................................................ iv
1 Cold polar molecules ......................................... 1
1.1 Applications of cold polar molecules .................... 2
1.1.1 Cold chemistry and cold collisions ............... 2
1.1.2 Quantum information science ...................... 4
1.1.3 Precision spectroscopy ........................... 5
1.2 Production of cold polar molecules ...................... 6
1.2.1 Indirect methods: Forging molecular bonds
between ultracold atoms .......................... 7
1.2.2 Direct methods: Controlling translational and
internal molecular motion ........................ 8
1.3 Approach of the Rempe group to produce cold
molecules .............................................. 11
1.3.1 History, developments, and extensions of the
electric guide .................................. 11
1.4 This thesis ............................................ 13
2 Electrostatic velocity filtering and guiding of polar
molecules ................................................... 15
2.1 Theory of electrostatic velocity filtering of polar
molecules .............................................. 16
2.1.1 Velocity distributions in the thermal source .... 18
2.1.2 Cutoff velocities in the electric guide ......... 18
2.1.3 Flux of guided molecules ........................ 19
2.2 Experimental setup ..................................... 19
2.3 Velocity-filtering experiments ......................... 21
2.4 The flux-density mystery ............................... 22
2.5 Velocity distribution of guided molecules .............. 26
3 Collisional effects in the formation of cold guided beams
of polar molecules .......................................... 29
3.1 Measurements of collisional effects .................... 29
3.2 Pressure dependence of velocity filtering .............. 30
3.3 Model of velocity filtering including collisional
losses ................................................. 33
3.4 Electrode-voltage dependence of velocity filtering ..... 35
3.5 Velocity distributions of guided molecules ............. 38
3.6 Summary ................................................ 40
4 Cold guided beams of water isotopologs ...................... 41
4.1 Stark shift of the water isotopologs ................... 42
4.1.1 Calculation of Stark shifts ..................... 43
4.1.2 Discussion of Stark shifts ...................... 48
4.2 Calculation of the flux of guided molecules ............ 55
4.3 Experimental procedure ................................. 57
4.4 Electrode-voltage dependence ........................... 60
4.5 Velocity distributions ................................. 62
4.6 Summary ................................................ 64
5 Internal-state thermometry by depletion spectroscopy ........ 67
5.1 Experimental setup ..................................... 68
5.2 Room-temperature absorption spectroscopy of
formaldehyde ........................................... 70
5.2.1 Formaldehyde-spectroscopy setup ................. 70
5.2.2 Results and discussion .......................... 73
5.3 Internal-state distribution of guided formaldehyde
molecules .............................................. 77
5.3.1 Depletion spectroscopy of individual
rotational states ............................... 77
5.3.2 Internal-state distribution in the guided
beam ............................................ 80
5.4 Summary ................................................ 82
6 Cavity-enhanced Rayleigh scattering ......................... 83
6.1 Experimental setup ..................................... 85
6.2 Cavity mode spectrum ................................... 87
6.3 Classical wave-interference model of cavity
enhancement ............................................ 89
6.3.1 The intracavity field ........................... 89
6.3.2 Comparison to free-space scattering: The
Purcell factor .................................. 91
6.4 Cavity-finesse dependence of Rayleigh scattering ....... 95
6.4.1 Influence of the cavity finesse on the
spectral profiles ............................... 95
6.4.2 Cavity-finesse dependence of the scattered
power ........................................... 96
6.5 Summary ................................................ 97
7 Outlook ..................................................... 99
7.1 Extensions and applications of electrostatic
velocity filtering and guiding ........................ 100
7.1.1 Spectroscopy of cold molecules ................. 100
7.1.2 Collision experiments with cold molecules ...... 101
7.2 Ongoing developments in the Rempe group ............... 102
7.2.1 Electrostatic extraction of molecules from
a cryogenic buffer-gas source .................. 103
7.2.2 Opto-electrical cooling of polar molecules ..... 105
A Guiding-efficiency reconstruction for the different water
isotopologs ................................................ 107
A.l Concentrations of water isotopologs injected into
the quadrupole guide .................................. 107
A.2 Detection of cold guided water isotopologs ............ 111
Bibliography .................................................. 115
List of Publications .......................................... 137
Danksagung .................................................... 139
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