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Chiral metamaterials are obtained by assembling plasmonic elements in geometries with broken mirror symmetry, which can have promising applications pertaining to generation, manipulation and detection of optical polarisation. The materials used to fabricate this promising nanosystem, especially in the visible-NIR regime, are limited to noble metals such as Au and Ag. However, they are not stable at elevated temperatures and in addition, incompatible with CMOS technologies. We demonstrate that it is possible to develop a chiro-plasmonic system based on a refractory material such as titanium nitride (TiN) which does not have these disadvantages. The building block of our metamaterial is a novel core-shell helix, obtained by coating TiN over silica nanohelices. These were arranged in a regular two-dimensional array over cm-scale areas, made possible by the use of scalable fabrication techniques such as laser interference lithography, glancing angle deposition and DC magnetron sputtering. The measured chiro-optical response was extremely broadband (<500 nm to >1400 nm), and had contributions from individual, as well as collective plasmon modes of the interacting nanohelices, whose spectral characteristics could be easily controlled by varying the direction of the incident radiation.

Improved optical control of molecular quantum states promises new applications including chemistry in the quantum regime, precision tests of fundamental physics, and quantum information processing. While much work has sought to prepare ground state molecules, excited states are also of interest. Here, we demonstrate a broadband optical approach to pump trapped SiO+ molecules into pure super rotor ensembles maintained for many minutes. Super rotor ensembles pumped up to rotational state N = 67, corresponding to the peak of a 9400 K distribution, had a narrow N spread comparable to that of a few-kelvin sample, and were used for spectroscopy of the previously unobserved C2Π state. Significant centrifugal distortion of super rotors pumped up to N = 230 allowed probing electronic structure of SiO+ stretched far from its equilibrium bond length.

Optical pumping of molecules provides unique opportunities for control of chemical reactions at a wide range of rotational energies. This work reports a chemical reaction with extreme rotational excitation of a reactant and its kinetic characterization. We investigate the chemical reactivity for the hydrogen abstraction reaction SiO+ + H2 → SiOH+ + H in an ion trap. The SiO+ cations are prepared in a narrow rotational state distribution, including super-rotor states with rotational quantum number (j) as high as 170, using a broad-band optical pumping method. We show that the super-rotor states of SiO+ substantially enhance the reaction rate, a trend reproduced by complementary theoretical studies. We reveal the mechanism for the rotational enhancement of the reactivity to be a strong coupling of the SiO+ rotational mode with the reaction coordinate at the transition state on the dominant dynamical pathway.

SiO + was proposed as a candidate for ultracold molecule experiments. Cooling schemes required to prepare SiO + in its ground state require knowledge of state energies, lifetimes and branching of selected SiO + transitions. Knowledge of dissociative transitions is needed to probe state populations of SiO + in the proposed experiments. Finally, efficient loading of SiO + into a trap by photoionization requires studying spectroscopy of neutral SiO. In this talk, I will discuss recent progress in study of SiO and SiO + spectroscopy in our lab and approaches used to address these studies.

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Optical pumping of molecules provides unique opportunities for control of chemical reactions at a wide range of rotational energies. Chemical reactivity for the hydrogen abstraction reaction SiO + + H2 → 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 (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.

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