ABSTRACT The one-particle density in momentum space g. p is studied for diatomic molecules byusing the maximum-entropy technique. The knowledge of one or more momentumexpectation values ˆ p n :.provides approximations on the density g for any value ofthe momentum, which are convergent when increasing the number of known moments.Other unknown expectation values are estimated in terms of the constructed maximum-entropy densities. A numerical study of the quality of the approximations is carried outby means of experimental and theoretical data for the momentum expectation valuesinvolved. Experimental errors are also taken into account to have an idea of thesensibility of the results to the information from which they are obtained. Q 1997 JohnWiley & Sons, Inc.* Permanent address: Departamento de Matematica Apli- ´ cada, ETS Ingenieros Industriales, Universidad Politecnica de ´ Madrid, 28006-Madrid, Spain. † Permanent address: Departamento de Fisica Moderna, Fa- ´ cultad de Ciencias, Universidad de Granada, 18071-Granada,Spain.International Journal of Quantum Chemistry, Vol. 61, 77]83 1997()Q 1997 John Wiley & Sons, Inc. CCC 0020-7608 / 97 / 010077-07