FTIR spectra of the neutral L-Ascorbic acid (vitamin C) (L-AA) have been recorded in the range 50-4000 cm-1 on a Varian spectrometer model 3100 using KBr and Nujol optics with 2 cm-1 resolution. The computations were carried out by employing the RHF and DFT methods to investigate the optimized molecular geometries, atomic charges, thermodynamic properties and harmonic vibrational frequencies along with intensities in IR and Raman spectra and depolarization ratios of the Raman bands for the neutral L-AA and its singly charged anionic (L-AA-) and cationic (L-AA+) species. All the 54 normal modes of the L-AA molecule have been assigned and discussed in details in the present study. The bond lengths in the lactone ring for the 2 (C-O) bonds in L-AA- are found to increase whereas for L-AA+ these are found to be decrease as compared to the neutral molecule. The bond angles a(C-O-H) decreases in L-AA- but increases for L-AA+ as compared to the neutral molecule. The dihedral angle H-C-C-H increases by 12.4° while reverse change is noticed for the other H-C-C-H dihedral anglewhich decreases by 14.3° in going from L-AA to L-AA- . The magnitudes of the calculated frequencies for the d(C-H) modes n38 and n34 decrease by 37 and 27 cm-1 for L-AA- whereas increase 15 and 33 cm-1 for L-AA+ with respect to the neutral molecule. The radicalization of the neutral molecule shifts the magnitude of the frequency of the n(C-OH) mode n32 by ~30 cm-1 for L-AA- and by 20 cm-1 for L-AA+ and the IR intensity for the n32 mode decreases in going from L-AA to L-AA- to L-AA+.