Doppler and Sisyphus cooling of 174 YbOH are achieved and studied. This polyatomic molecule has high sensitivity to physics beyond the Standard Model and represents a new class of species for future high-precision probes of new T-violating physics. The transverse temperature of the YbOH beam is reduced by nearly two orders of magnitude to < 600 μK and the phase-space density is increased by a factor of > 6 via Sisyphus cooling. We develop a full numerical model of the laser cooling of YbOH and find excellent agreement with the data. We project that laser cooling and magneto-optical trapping of long-lived samples of YbOH molecules are within reach and these will allow a high sensitivity probe of the electric dipole moment of the electron. The approach demonstrated here is easily generalized to other isotopologues of YbOH that have enhanced sensitivity to other symmetryviolating electromagnetic moments.

Magneto-optical trapping forces for molecules are far weaker than for alkali atoms because the photon scattering rate is reduced when there are multiple ground states, and because of optical pumping into dark states. The force is further reduced when the upper state has a much smaller Zeeman splitting than the lower state. We use a rate model to estimate the strength of the trapping and damping forces in a magneto-optical trap (MOT) of CaF molecules, using either the A 2 Π 1/2 -X 2 Σ + transition or the B 2 Σ + -X 2 Σ + transition. We identify a new mechanism of magnetooptical trapping that arises when, in each beam of the MOT, two laser components with opposite polarizations and different detunings address the same transition. This mechanism produces a strong trapping force even when the upper state has little or no Zeeman splitting. It is the main mechanism responsible for the trapping force when the A 2 Π 1/2 -X 2 Σ + transition is used.

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Alkaline earth monoalkoxide free radicals (MORs) have molecular properties conducive to direct laser cooling to sub-millikelvin temperatures. Using dispersed laser induced fluorescence measurements from a pulsed supersonic molecular beam source we determine vibrational branching ratios and Franck-Condon factors for the MORs CaOH and CaOCH 3 . With narrow linewidth continuous-wave dye laser excitation, we precisely measure fluorescence branching for both X Ã -˜and X B -˜electronic systems in each molecule. Weak symmetry-forbidden decays to excited bending states with non-zero vibrational angular momentum are observed. Normal mode theoretical analysis combined with ab initio structural calculations are performed and compared to experimental results. Our measurements and analysis pave the way for direct laser cooling of these (and other) complex nonlinear polyatomic molecules. We also describe a possible approach to laser cooling and trapping of molecules with fewer symmetries like chiral species.

Supersonic molecular beam samples of iridium monocarbide IrC and iridium mononitride IrN were generated using a laser ablation/reaction source and characterized using high resolution (Δν&lt;30 MHz FWHM) laser induced fluorescence spectroscopy. This is the first identification of gaseous IrN. Numerous strong band systems in the 18 800 to 14 360 cm−1 spectral range were assigned as the (v′,0) progression of the A 1Π–X 1Σ+ band system of IrN. The (1,0) and (0,0) bands were analyzed to produce a set of fine and hyperfine parameters. The electric field induced effects on the R(0) line of these bands were analyzed to produce permanent electric dipole moments: A 1Π(v=0) 2.78(2) D, A 1Π(v=1) 2.64(2) D, X 1Σ+(v=0)=1.66(1) D. The (0,0) band of the D2 Φ7/2−X 2Δ5/2 system of IrC was recorded and analyzed to produce a set of fine and hyperfine parameters. The electric field induced effects on the R(2.5) branch feature were analyzed to produce permanent electric dipole moments: D 2Φ7/2(v=0) 2.61(6) D and X 2Δ5/2(v=0) 1.60(7) D. Plausible electronic configurations consistent with the experimental observations are given.

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A comparative study of the hyperfine interactions in the X 2Σ+ state of TiN and the X 3Δ state of TiO has been performed. The 48Ti14N(I=1) hyperfine structure was determined from the analysis of 19 components of the N=1–0 and N=2–1 pure rotational transitions recorded using the pump/probe microwave-optical double resonance technique. The 47Ti(I=5/2) hyperfine structure of X 2Σ+ TiN was determined from an analysis of the high resolution optical spectrum of the (0,0) A 2Π3/2–X 2Σ+ band system. The resulting parameters are (in MHz) B(48Ti14N)=18 589.3513(13), D(48Ti14N)=0.026 31(18), γ(48Ti14N)=−52.2070(13), bF(N)=18.480(3), c(N)=0.166(7), eQq0(N)=−1.514(8), CI(N)=0.0137(12), bF(47Ti) =−558.8(11), c(47Ti)=−15(5), and eQq0(47Ti)=62(16). An analysis of the (0,0) band of the B 3Π–X 3Δ system of 47Ti16O produced the X 3Δ hyperfine parameters (in MHz): a(47Ti) =−54.7(21), (bF+2c/3)(47Ti)=−231.6(60), and eQq0(47Ti)=−49(31). An interpretation based upon the predicted nature of the bonding in TiO and TiN is given.

The permanent electric dipole moments of the ground, and the low-lying excited electronic states of platinum monocarbide, PtC, platinum monoxide, PtO, and platinum monosulfide, PtS, were measured using a molecular beam optical Stark spectroscopic scheme. The determined values were (in Debye): PtO(X 3Σ−) 2.77(2); PtO(A 1Σ+) 1.15(4); PtS[X(Ω=0)] 1.78(2); PtS[B(Ω=0)] 0.54(6); PtC(X 1Σ+) 0.99(5); and PtC(A 1Π) 2.454(3). These results, along with the previous results for PtN(X 2Π1/2) 1.977(9); PtN(d 4Π1/2) 1.05(9) [J. Chem. Phys. 102, 643 (1995)], are used as a basis for a discussion of the nature of the electronic states.