PROGRESS ON OPTICAL ROTATIONAL COOLING OF SiO+

Producing ultracold molecules is the first step in precision molecular spectroscopy. Here we present some of the challenges and advantages of SiO+ as well as some of our progress toward meeting those challenges. To demonstrate ground state SiO+, we first load about 100 SiO+ via 2+1 REMPI into an ion trap. Translational motion of SiO+ is then sympathetically cooled by co-trapped Ba+, which is laser cooled. To prepare the population into the ground state, we optically pump the P-branch (rotational cooling transitions) in the B:$Sigma$(v�=0) $leftarrow$ X:$Sigma$(v=0) band with broadband radiation. Because the band is highly diagonal, population can be effectively driven into the rotational ground state before falling into other manifolds. The broadband source, a fs laser, is spectrally filtered using an ultrashort pulse shaping technique to drive only the P-branch. Attention must be paid when aligning the optics to obtain sufficient masking resolution. We have achieved 3 cm$^{-1}$ resolution, which is sufficient to modify a broadband source for rotationally cooling SiO+

Optical Pumping of TeH+: Implications for the Search for Varying mp/me

Molecular overtone transitions provide optical frequency transitions sensitive to variation in the proton-to-electron mass ratio ($\mu\equiv m_p/m_e$). However, robust molecular state preparation presents a challenge critical for achieving high precision. Here, we characterize infrared and optical-frequency broadband laser cooling schemes for TeH$^+$, a species with multiple electronic transitions amenable to sustained laser control. Using rate equations to simulate laser cooling population dynamics, we estimate the fractional sensitivity to $\mu$ attainable using TeH$^+$. We find that laser cooling of TeH$^+$ can lead to significant improvements on current $\mu$ variation limits

Rotational control of reactivity: Reaction of SiO+^+ ions in extreme rotational states

Optical pumping of molecules provides unique opportunities for the control of chemical reactions at a wide range of rotational energies. Chemical reactivity for the hydrogen abstraction reaction SiO$^+$ + H$_2$ $\rightarrow$ SiOH$^+$ + H is investigated in an ion trap. The SiO$^+$ cation is prepared with a narrow rotational state distribution, including super-rotor states with rotational quantum number $\it{(j)}$ as high as 170 using a broad-band optical pumping method. The super-rotor states of SiO$^+$ are shown to substantially enhance the reaction rate, a trend reproduced by complementary theoretical studies. The mechanism for the rotational enhancement of the reactivity is revealed to be a strong coupling of the SiO$^+$ rotational mode with the reaction coordinate at the transition state on the dominant dynamical pathway. This work reports for the first time a chemical reaction with extreme rotational excitation of a reactant and its kinetic characterization

COLECCIONES FOTOGRÁFICAS DEL MUSEO Y PARQUE ARQUEOLÓGICO CUEVA PINTADA [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria, 201