A molecular dynamics simulation is performed for a supercooled liquid ofrigid diatomic molecules. The time-dependent self and collective densitycorrelators of the molecular centers of mass are determined and compared withthe predictions of the ideal mode coupling theory (MCT) for simple liquids.This is done in real as well as in momentum space. One of the main results isthe existence of a unique transition temperature T_c, where the dynamicscrosses over from an ergodic to a quasi-nonergodic behavior. The value for T_cagrees with that found earlier for the orientational dynamics within the errorbars. In the beta- regime of MCT the factorization of space- and timedependence is satisfactorily fulfilled for both types of correlations. Thefirst scaling law of ideal MCT holds in the von Schweidler regime, only, sincethe validity of the critical law can not be confirmed, due to a stronginterference with the microscopic dynamics. In this first scaling regime aconsistent description within ideal MCT emerges only, if the next ordercorrection to the asymptotic law is taken into account. This correction isalmost negligible for q=q_max, the position of the main peak in the staticstructure factor S(q), but becomes important for q=q_min, the position of itsfirst minimum. The second scaling law, i.e. the time-temperature superpositionprinciple, holds reasonably well for the self and collective densitycorrelators and different values for q. The alpha-relaxation times tau_q^(s)and tau_q follow a power law in T-T_c over 2 -- 3 decades. The correspondingexponent gamma is weakly q-dependent and is around 2.55. This value is inagreement with the one predicted by MCT from the value of the von Schweidlerexponent but at variance with the corresponding exponent gamma
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