  In 1998, we have given in ([14] Intissar, A., Analyse de Scattering d'un
op\'erateur cubique de Heun dans l'espace de Bargmann, Comm.Math.Phys.199
(1998) 243-256) the boundary conditions at infinity for a description of all
maximal dissipative extensions in Bargmann space of the minimal Heun's operator
$H_I = z(\frac{d}{dz} + z)\frac{d}{dz}$; $z \in \mathbb{C}$. The characteristic
functions of the dissipative extensions have computed and some completeness
theorems have obtained for the system of generalized eigenvectors. In ([18]
Intissar, A, Le Bellac, M. and Zerner, M., Properties of the Hamiltonian of
Reggeon field theory, Phys. Lett. B 113 (1982) 487-489) the non self-adjoint
operator $\lambda H_{I}$ where $\lambda \in \mathbb{R}$ is imaginary part of
the Hamiltonian of Reggeon field theory: $$H_{\mu, \lambda} = \mu z\frac{d}{dz}
+ i \lambda z( \frac{d}{dz} + z)\frac{d}{dz} \,\, \text{where} \,\, (\mu,
\lambda) \in \mathbb{R}^{2} \,\, \text{and} \,\, i^{2} = -1$$ The main purpose
of the present work is to present some new spectral properties of right inverse
$K_{0, \lambda}$ of $H_{\lambda} = i\lambda H_I$ ($H_{\lambda}K_{0, \lambda} =
I$) on negative imaginary axis and to study the deficiency numbers of the
generalized Heun's operator $H^{p,m} = z^{p}( \frac{d^{m}}{dz^{m}} +
z^{m})\frac{d^{p}}{dz^{p}}$ $p, m = 1, 2, ....$. In particular, here we find
some conditions on the parameters $p$ and $m$ for that $H_{I}^{p,m}$ to be
completely indeterminate.It follows from these conditions that $H^{p,m}$ is
entire of the type minimal.
