Multiple source and detection frequencies in detecting threshold phenomena associated with and/or atomic or molecular spectra

A method for detecting threshold phenomena associated with and/or atomic or molecular spectra of at least two substances in the vicinity of each other, comprising:

• providing a time varying electrical signal, said signal including components of at least two different frequencies, wherein said at least two frequencies individually or in combination are characteristic of said at least two substances;
• coupling the signal to said at least two substances;
• and
• substantially simultaneously measuring the amplitudes of the current or voltage across the substances at said at least two frequencies or their harmonics, or their sums and differences or combinations thereof to detect threshold phenomena associated with and/or atomic or molecular spectra of the at least two substances.

An apparatus for detecting threshold phenomena associated with and/or atomic or molecular spectra of at least one substance, comprising:

• a source providing a time varying electrical signal, said signal including components of at least two different frequencies, said source including at least two signal generators each providing an electrical signal with frequencies in a frequency band including one of the at least two frequencies, and a combiner or mixer connecting the generators;
• electrodes for coupling the signal to said at least one substance;
• and
• a device substantially simultaneously measuring the amplitudes of the current or voltage across the substance at frequencies including said at least two frequencies or combinations thereof.

A method for detecting threshold phenomena associated with and/or atomic or molecular spectra of at least one substance, comprising:

• providing time varying electrical signals of at least two different frequencies;
• combining or mixing said signals;
• coupling the combined or mixed signals to said at least one substance;
• and
• substantially simultaneously measuring the amplitudes of the current or voltage across the substances at frequencies including said at least two frequencies or combinations thereof.