If I am not mistaken, the first observation of the molecular orbital was described in Nature 432, 867-871 (doi 10.1038/nature03183).

"When the orbital approach is used in an attempt to answer a chemical question, there can be as many different answers as there are attempts."

Bader (2005) Monatshefte für Chemie / Chemical Monthly 136: 819-854.

https://link.springer.com/article/10.1007/s00706-005-0307-x

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"Atoms in Molecules"

http://www.chemistry.mcmaster.ca/aim/aim_0.html

Molecular orbitals are a purely mathematical construct, they do not exist (with exception for hydrogen atom)

orbital is not the physical body, it is a mathematical function that is written on paper. As for the function, we can draw its graph. But they do not exist in nature.

There are no p, d, f ... orbitals in an atom. Atoms are spherically symmetric ones. This is an experimental fact.

Refer to the work by Paul B. Corkum and David M. Villeneus (NRC/Ottawa/Canada) Sci. Am. April 18, In Focus, 2005.

In a quantum mechanical framework, (molecular) orbitals do not belong to the class of observable entities. Hence, there is nothing like a "photography" of any orbital. By definition, orbitals, be it atomic or molecular, are solutions of a single-electron Schrödinger equation. However, the electron density, which can be calculated from the wave function of an atom or molecule is an observable. Wave functions of atoms and molecules can be approximated by linear combinations of orbitals. Accordingly, orbitals are seen as "basis functions" for representing the wave function and have only limited physical meaning with respect to the look of atoms and molecules. Electron density, however, can be visualized. E.g., x-ray scattering (crystallography) and scanning tunneling electron microscopy (STM) of isolated atoms and molecules on appropriate substrates can produce images of electron density and its variation in molecular frameworks. STM dates back to the early 80th and was invented by Binning and Rohrer (Physics Nobel Prize in 1986). 

I am attaching some papers on observing molecular orbitals for all who are following the question