As front-line theories to control spin dynamics in solid-state nuclear magnetic resonance, the Average Hamiltonian Theory (AHT) [1] and Floquet Theory (FLT) [2,3] have assumed great prominence and influence since the development of multiple pulse sequences and the inception of Magic-Angle Spinning (MAS) methods in the 1960s [4,5]. Methods developed over the past decade have enabled us to make a significant progress in the area of NMR by introducing an alternative expansion scheme called Floquet-Magnus Expansion (FME) [6,7] used to solve the time-dependent Schrodinger equation which is a central problem in quantum physics in general and solid-state NMR in particular. The FME establish the connection between the Magnus Expansion (ME) and the Floquet theory, and provides a new version of the ME well suited for the Floquet theory for linear ordinary differential equations with periodic coefficients [6][7][8][9][10][11][12]. We have proved that the ME is a particular case of the FME which yields new aspects not present in ME and Floquet theory such as recursive expansion scheme in Hilbert space that can facilitate the implementation of new or improvement of existing pulse sequences [6]. In the same vein, Madhu and Kurur has recently introduced the Fer Expansion (FE) in Solid-State NMR [13,14]. The Fer expansion was formulated by Fer [13] and later revised by Fer [13], Klarsfeld and Oteo [15], Casas, et al. [16] and Blanes, et al. [17]. This expansion employs the form of a product of sub-propagators, which appears to be suitable for examination of time-dependence of the density matrix for each average Hamiltonian at different orders. A paper which outlines the comparison of both theories (FME and FE) in NMR and physics has recently been published in the Journal of Physical Chemistry A [18].

Globalization and ecological disruption associated with newly emerging infectious diseases, and with reemerging infections previously thought to be under control can lead to the surge of an unexpected pandemic, which is evident throughout the world with the appearance of the COVID-19 pandemic. The newly emerged havoc-inducing disease COVID-19 is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) [1]. The major escalation of the disease is conventionally trailed back to January of 2020 in the Chinese province of Hubei, the wet markets of the principal city of Wuhan which is presumed to be the specific inventive location of the sudden eruption of the infection [2]. Authorities in 217 countries and territories have reported about 81.5 million Covid-19 cases and 1.8 million deaths since China reported its first cases to the World Health Organization (WHO) in December 2019 [3]. COVID-19 is a member of the Coronaviridae (CoV) subfamily of the Coronavirinae family, which belongs to the order Nidovirales. The subfamily consists of 40 varieties of single-stranded RNA-viruses existing in bats and wild birds, which can develop to infect humans and non-human mammals and birds. Due to their capability to recombine, mutate, and infect multiple species and cell