A Complex function which is a linear combination of Bessel Functions of the First and Second Kinds.
See also Hankel Function of the First Kind, Hankel Function of the Second Kind, Spherical Hankel Function of the First Kind, Spherical Hankel Function of the Second Kind
References
Arfken, G. ``Hankel Functions.'' §11.4 in Mathematical Methods for Physicists, 3rd ed.
Orlando, FL: Academic Press, pp. 604-610, 1985.
Morse, P. M. and Feshbach, H. Methods of Theoretical Physics, Part I. New York: McGraw-Hill, pp. 623-624, 1953.