Dilithium

<p>Dilithium, Li2, is a strongly <a href="/facts/Electrophile/1AHFg1zm">electrophilic</a>, <a href="/facts/Diatomic/hkfKAC7m">diatomic</a> molecule comprising two <a href="/facts/Lithium/7vXX6BWA">lithium</a> <a href="/facts/Atom/FoQ4kGN5">atoms</a> <a href="/facts/Covalent_bond/EzMLf3Pz">covalently bonded</a> together.  Li2 has been observed in the <a href="/facts/Gas/hVVAoodV">gas</a> <a href="/facts/Phase_(matter)/NkHXDdN3">phase</a>. 
It has a <a href="/facts/Bond_order/Tdb1zgTc">bond order</a> of 1, an internuclear separation of 267.3 <a href="/facts/Picometre/Cb54mVBX">pm</a> and a <a href="/facts/Bond_energy/q4be3EeR">bond energy</a> of 102 kJ/mol or 1.06 eV in each bond. 
The <a href="/facts/Electron_configuration/TQjRr22P">electron configuration</a> of Li2 may be written as σ2.
</p><p>Being the third-lightest stable neutral <a href="/facts/Homonuclear_molecule/Pn0bshdv">homonuclear</a> <a href="/facts/Diatomic_molecule/hkfKAC7m">diatomic molecule</a> (after <a href="/facts/Dihydrogen/BoYHjl0J">dihydrogen</a> and <a href="/facts/Dihelium/w0vNKr2p">dihelium</a>), dilithium is an extremely important model system for studying fundamentals of physics, chemistry, and <a href="/facts/Ab_initio_quantum_chemistry_methods/Rwuu2At1">electronic structure theory</a>.
</p><p>It is the most thoroughly characterized compound in terms of the accuracy and completeness of the empirical <a href="/facts/Morse%2fLong-range_potential/TI1GX5bn">potential energy curves</a> of its electronic states. Analytic empirical potential energy curves have been constructed for the X-state, a-state, A-state, c-state, B-state, 2d-state, l-state, E-state, and the F-state. The most reliable of these potential energy curves are of the <a href="/facts/Morse%2fLong-range_potential/TI1GX5bn">Morse/Long-range</a> variety (see entries in the table below).
</p><p>Li2 potentials are often used to extract atomic properties. For example, the C3 value for atomic lithium extracted from the A-state potential of Li2 by Le Roy et al. in  is more precise than any previously measured atomic oscillator strength. 
This lithium oscillator strength is related to the radiative lifetime of atomic lithium and is used as a benchmark for atomic clocks and measurements of fundamental constants.
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<table><tbody><tr><th><a href="/facts/Electronic_state/66x51Khc">Electronic state</a></th><th>Spectroscopic symbol</th><th><a href="/facts/Molecular_term_symbol/plQdFUQX">Term symbol</a></th><th colspan="2"><a href="/facts/Bond_length/rHHIBH6q">Bond length</a> (pm)</th><th colspan="2">Dissociation energy (cm−1)</th><th>Bound vibrational levels</th><th>References</th></tr><tr><td>1 (Ground)</td><td>X</td><td>11Σg+</td><td>267</td><td>.298 74(19)</td><td>8 516</td><td>.780 0(23)</td><td>39</td><td></td></tr><tr><td>2</td><td>a</td><td>13Σu+</td><td>417</td><td>.000 6(32)</td><td>333</td><td>.779 5(62)</td><td>11</td><td></td></tr><tr><td>3</td><td>b</td><td>13Πu</td><td colspan="2"></td><td colspan="2"></td><td></td><td></td></tr><tr><td>4</td><td>A</td><td>11Σg+</td><td>310</td><td>.792 88(36)</td><td>9 353</td><td>.179 5 (28)</td><td>118</td><td></td></tr><tr><td>5</td><td>c</td><td>13Σg+</td><td>306</td><td>.543 6(16)</td><td>7 093</td><td>.492 6(86)</td><td>104</td><td></td></tr><tr><td>6</td><td>B</td><td>11Πu</td><td>293</td><td>.617 142(310)</td><td>2 984</td><td>.444</td><td>118</td><td></td></tr><tr><td>7</td><td>E</td><td>3(?)1Σg+</td><td colspan="2"></td><td colspan="2"></td><td></td><td></td></tr></tbody></table>

Dilithium open-in-new

Dilithium