We report on the spectroscopic and laser characterization of negatively charged nitrogen-vacancy (NV-) centers in diamond. Spectroscopic properties such as absorption and emission spectra as well as kinetics were studied, and parameters such as cross-sections and lifetimes were estimated. A vibronic band of NV0 with zero phonon line (ZPL) at 575 nm was detected under 532 nm pulsed excitation due to the photoionization of NV-. Transmission of 532 nm pump pulses saturate around ~10%, which is much smaller than the theoretical level. Δk/k0 kinetics revealed slow recovery of NV- centers after photoionization under 532 nm pumping, which involved different relaxation channels depending on the probe beam wavelengths. Localization of the electrons in the metastable state of NV0 centers resulted in higher saturated transmission of 632 nm pump.