Nuclear Quadrupole Resonance (NQR) provides spectra carrying information
as to the electric-field gradient around nuclei with a spin quantum number I > 1/2
and offers helpful clues toward characterizing the electronic structure of materials
of chemical interest. A major challenge in NQR is finding hitherto unknown resonance frequencies, which can scatter over a wide range, requiring time consuming
repetitive measurements with stepwise frequency increments. Here, we report on
an efficient, two-step NQR protocol by bringing rapid-scan and frequency-comb together. In the first step, wideband excitation and simultaneous signal acquisition,
both realized by a non-adiabatic, frequency-swept hyperbolic secant (HS) pulse
with comb modulation, offers a clue for the existence/absence of the resonance
within the frequency region under investigation. When and only when the sign of
the resonance has been detected, the second step is implemented to compensate
the limited detection bandwidth of the first and to unambiguously determine the
NQR frequency. We also study the spin dynamics under the comb-modulated HS
pulse by numerical simulations, and experimentally demonstrate the feasibility of
the proposed scheme, which is referred to as RApid-Scan with GApped excitation
with Dual-mode Operation (RASGADO) NQR<br>
Ab initio calculations of nuclear quadrupole resonance frequencies in trichloroacetyl halides: a comparison of DFT and experimental data
