| Summary: | The creation of a combined radiative state at 2.95–3.1 eV in the phosphor <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>C</mi><mi>a</mi><mi>S</mi><mi>O</mi></mrow><mrow><mn>4</mn></mrow></msub><mo>−</mo><msubsup><mrow><mi>D</mi><mi>y</mi></mrow><mrow><mo> </mo></mrow><mrow><mn>3</mn><mo>+</mo></mrow></msubsup></mrow></semantics></math></inline-formula> has been investigated using vacuum ultraviolet and thermoactivation spectroscopy methods. It is shown that the combined radiative electronic state is formed from the radiative electronic states of the impurity electronic trapping centers <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mrow><mi>D</mi><mi>y</mi></mrow><mrow><mo> </mo></mrow><mrow><mn>2</mn><mo>+</mo></mrow></msubsup><mo>−</mo><msubsup><mrow><mo> </mo><mi>S</mi><mi>O</mi></mrow><mrow><mn>4</mn></mrow><mrow><mo>−</mo></mrow></msubsup></mrow></semantics></math></inline-formula> and the intrinsic electronic radiative states <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mrow><mi>S</mi><mi>O</mi></mrow><mrow><mn>4</mn></mrow><mrow><mn>3</mn><mo>−</mo></mrow></msubsup><mo>−</mo><msubsup><mrow><mi>S</mi><mi>O</mi></mrow><mrow><mn>4</mn></mrow><mrow><mo>−</mo></mrow></msubsup></mrow></semantics></math></inline-formula> during the excitation of the anion complex <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mrow><mi>S</mi><mi>O</mi></mrow><mrow><mn>4</mn></mrow><mrow><mn>2</mn><mo>−</mo></mrow></msubsup></mrow></semantics></math></inline-formula>, as a result of charge transfer from the excited anion complex <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mrow><mi>O</mi></mrow><mrow><mo> </mo></mrow><mrow><mn>2</mn><mo>−</mo></mrow></msubsup><mo>−</mo><msubsup><mrow><mi>D</mi><mi>y</mi></mrow><mrow><mo> </mo></mrow><mrow><mn>3</mn><mo>+</mo></mrow></msubsup></mrow></semantics></math></inline-formula> to the impurities and the neighboring anion complex <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mi>O</mi></mrow><mrow><mn>2</mn><mo>−</mo></mrow></msup><mo>−</mo><msubsup><mrow><mo> </mo><mi>S</mi><mi>O</mi></mrow><mrow><mn>4</mn></mrow><mrow><mn>2</mn><mo>−</mo></mrow></msubsup></mrow></semantics></math></inline-formula>. In the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>C</mi><mi>a</mi><mi>S</mi><mi>O</mi></mrow><mrow><mn>4</mn></mrow></msub><mo>−</mo><mi>D</mi><mi>y</mi></mrow></semantics></math></inline-formula> phosphor, the combined radiative electronic state and impurity emission of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mrow><mi>D</mi><mi>y</mi></mrow><mrow><mo> </mo></mrow><mrow><mn>3</mn><mo>+</mo></mrow></msubsup></mrow></semantics></math></inline-formula>, 2.16 eV and 2.56 eV are excited by photons with energies of 3.95–4.0 eV and 4.5–4.6 eV. Energy transfer from the matrix to the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mrow><mi>D</mi><mi>y</mi></mrow><mrow><mo> </mo></mrow><mrow><mn>3</mn><mo>+</mo></mrow></msubsup></mrow></semantics></math></inline-formula> impurities is revealed upon thermal exposure as a result of the ionization of the electronic capture centers of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mi>D</mi><mi>y</mi></mrow><mrow><mn>2</mn><mo>+</mo></mrow></msup></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mrow><mi>S</mi><mi>O</mi></mrow><mrow><mn>4</mn></mrow><mrow><mn>3</mn><mo>−</mo></mrow></msubsup></mrow></semantics></math></inline-formula>.
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