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Micro-electric discharge machining (micro-EDM) has evolved as one of the prominent processes to generate high-aspect-ratio and accurate micro-structures in many industrial applications. This paper presents an extensive experimental analysis of the micro-EDM process to explore the relationship between accuracy as a function of depth of micro-holes drilled using micro-EDM drilling. It is shown that a depth of 5.0 mm can be achieved by a 200 μm diameter tool electrode while controlling the regular process parameters, but beyond this length, the process is governed by a number of derived phenomena such as secondary sparking, debris accumulation, etc. instead of the regular processing parameters. The optimum depth of the hole that could be achieved with a good accuracy i.e. a minimum oversize lies between 2.5 and 5.0 mm, the largest depth that could be achieved was 8.33 mm. The highest aspect ratio achieved in this experiment was 15.63.

Time-resolved resonance Raman (TR3) and density functional theoretical (DFT) studies on the photogenerated transient intermediates of tetrabromo-p-benzoquinone (bromanil) are reported. The lowest triplet excited state, radical anion, and semiquinone radical have been observed. Computed spectra and normal-coordinate analysis have been used to make assignments of the observed bands. The lowest triplet state is computed to be a π−π* excited state of ³Bg symmetry. The effect of electronic excitation on the triplet state structure is found to be more pronounced in bromanil as compared to that in p-benzoquinone. The changes in structure in the bromanil radical anion have been explained from the nodal structure of the LUMO of the ground state. The computed structure of the semiquinone radical shows that it is essentially a pentadienyl radical. Consequences of these structural changes on the observed vibrational spectra have been discussed.

IR and Raman spectra of DMABN (4-dimethylaminobenzonitrile) and its ring deuterated isotopomer DMABN-d₄ have been measured. Hartree–Fock (HF/6-31G*) and density function theory (DFT, B3LYP/6-31G*) ab initio calculations have been performed to interpret the observed vibrational spectra and isotopic shifts. Assignments of several controversial bands have been made. A large change of vibrational composition and mode pattern upon ring deuteration has been found for bands that have dominant contributions from the Wilson 19a, 19b, ν(Ph–N) and ν(Ph–CN) vibrations in DMABN.