Experimental studies of the sodium cesium 5(3)Pi(0) and 1(a)3Sigma+ electronic states

This dissertation describes a series of experiments designed to map out several electronic states of the NaCs molecule, which is of great current interest in the ultra-cold molecule community. A mixture of sodium and cesium was heated to a temperature of 290--320°C in a heat pipe oven to create NaCs molecules. The optical-optical double resonance (OODR) method was used to obtain Doppler-free excitation spectra of several excited electronic states. The Rydberg Klein Rees (RKR) and inverted perturbation approach (IPA) methods were applied to the 5 3pi0 ro-vibrational data to construct a potential curve for that electronic state.;The pump laser in the double resonance excitation scheme is a single-mode, continuous wave (cw) titanium-sapphire (Ti:Sapphire) laser pumped by an argon-ion laser. The pump laser excites the NaCs molecule out of a thermally populated ground state level to a mixed character (singlet-triplet) intermediate level on the transition 1(b) 3pi0( vb, J) ∼ 2(A) 1Sigma+(vA, J) ← 1(X) 1Sigma+ (v X, J +/-1). The counter-propagating probe laser is a single-mode, cw dye laser pumped by a krypton-ion laser. The probe laser further excites the molecules to high-lying triplet state levels through the transitions 5 3pi0 (v, J +/- 1) ← 1(b) 3pi 0 (vb, J) ∼ 2( A) 1Sigma+ (vA, J). 407 ro-vibrational levels belonging to the 5 3pi 0 electronic state with vibrational quantum numbers in the range v = 0--36 and rotational quantum numbers J = 1--84 have been observed. For over 100 of these ro-vibrational levels, bound-free 5 3pi0 (v, J) → 1(a) 3Sigma+ spectra have been recorded using a filtered 0.3 meter McPhereson monochromator equipped with a photomultiplier tube (PMT). Collisional progressions were used to greatly expand the data set and to aid in assigning rotational ( J) quantum numbers.;The repulsive wall of the 1(a) 3Sigma + state was mapped by comparing simulated and experimental bound-free fluorescence spectra. The shallow bound portion of the 1(a) 3Sigma+ potential was previously determined experimentally by Docenko et al. (2006) [3]. The repulsive wall constructed using our bound-free 5 3pi0 (v, J) → 1(a) 3Sigma+ resolved fluorescence spectra was made to attach smoothly and continuously to the shallow well of Docenko et al. Using a version of BCONT [5] modified by B. McGeehan [6], a global fit of the 1(a) 3Sigma + repulsive wall and 5 3pi0 ( v, J) → 1(a) 3Sigma + transition dipole moment was performed, simultaneously fitting 14 bound-free spectra spanning the range v = 0--22.;Hyperfine splitting in alkali diatomic molecules is dominated by the Fermi contact term Ehfs = bF I&ar;˙S&ar; . Cesium has a relatively large nuclear spin of 72 , and a large Fermi contact constant bF = 2298MHz, suggesting the hyperfine splitting of alkali diatomics containing Cs may be rather large. Because the NaCs molecule has a large spin-orbit interaction due to the cesium atom, it is best described using Hund's case (c) notation for states where spin-orbit coupling dominates. We derived models to predict the size of the hyperfine splitting for the limiting Hund's coupling cases (abeta) and (cbeta) and compared them to a similar model for case (bbetaJ). These models represent our current understanding of why the hyperfine splitting of NaCs triplet states has not yet been resolved.