22-08-2012, 12:46 PM
DEGREE OF FREEDOM
[attachment=32391]
In a molecule, the atoms are forced by molecular bonds to shift together in definite particular ways, is called degree of freedom.
DESCRIPTION:
When an exact molecular structure is identified its limitation allows supposition of expected molecular transitions. In order to explain degree of freedom of any molecule first of all the molecule is located in a three dimensional Cartesian coordinate system (x, y and z), with its center at the point of origin (0, 0, 0).Then assign each atom by its coordinates in space (i.e. , atom 1 =x1, y1, z1).
For a molecule with N atoms, where N is the any number, the total number of coordinates (xn, yn, Zn) specific will be 3N.
These 3N coordinates are the maximum number of potential transition infatuated by that molecule and are called its degree of freedom.
EXAMPLE:
For a molecule with 5 atoms has 15 degree of freedom the 3N degrees of freedom can be assigned to the translational rotational and vibration motions of the molecules. All molecules have translational degree of freedom that is, the center of mass of the molecule can move in three directions (x, y and z) if the molecule is nonlinear, then it also has three rotational degrees of freedom as it spins around each of the three axes (x, y and z).
Linear molecules have only two rotational degrees of freedom, since two rotation directions are equivalent. Thus the total of translational and rotational degrees of freedom is 6 (5 for linear molecule) all remaining motions, 3N-6, is vibration degree of freedom (f3N-5 in the case: the case of linear molecule) Degrees of freedom corresponding to type of motion for any molecule with N atoms. The total number of degrees of freedom for any molecule is 3N.If the motion is translational according to position of molecule the degree of freedom is 3.And if the motion of the molecule is rotational about the center of the molecule the degree of freedom is 3 for nonlinear and 2 for linear and in the case of vibration 3N-6 for nonlinear molecule and (3N-5 ) for linear molecule
FACTORS AFFECTING A REDUCTION IN NUMBER OF ABSORBTON BANDS:
i. Degeneracy,
ii. Overlapping or weak absorption
iii. Vibrational modes
In order to increase the observed bands we must detect the weak or forbidden absorptions in which the change in the Vibrational level is greater than 1 and these are known as overtones.
[attachment=32391]
In a molecule, the atoms are forced by molecular bonds to shift together in definite particular ways, is called degree of freedom.
DESCRIPTION:
When an exact molecular structure is identified its limitation allows supposition of expected molecular transitions. In order to explain degree of freedom of any molecule first of all the molecule is located in a three dimensional Cartesian coordinate system (x, y and z), with its center at the point of origin (0, 0, 0).Then assign each atom by its coordinates in space (i.e. , atom 1 =x1, y1, z1).
For a molecule with N atoms, where N is the any number, the total number of coordinates (xn, yn, Zn) specific will be 3N.
These 3N coordinates are the maximum number of potential transition infatuated by that molecule and are called its degree of freedom.
EXAMPLE:
For a molecule with 5 atoms has 15 degree of freedom the 3N degrees of freedom can be assigned to the translational rotational and vibration motions of the molecules. All molecules have translational degree of freedom that is, the center of mass of the molecule can move in three directions (x, y and z) if the molecule is nonlinear, then it also has three rotational degrees of freedom as it spins around each of the three axes (x, y and z).
Linear molecules have only two rotational degrees of freedom, since two rotation directions are equivalent. Thus the total of translational and rotational degrees of freedom is 6 (5 for linear molecule) all remaining motions, 3N-6, is vibration degree of freedom (f3N-5 in the case: the case of linear molecule) Degrees of freedom corresponding to type of motion for any molecule with N atoms. The total number of degrees of freedom for any molecule is 3N.If the motion is translational according to position of molecule the degree of freedom is 3.And if the motion of the molecule is rotational about the center of the molecule the degree of freedom is 3 for nonlinear and 2 for linear and in the case of vibration 3N-6 for nonlinear molecule and (3N-5 ) for linear molecule
FACTORS AFFECTING A REDUCTION IN NUMBER OF ABSORBTON BANDS:
i. Degeneracy,
ii. Overlapping or weak absorption
iii. Vibrational modes
In order to increase the observed bands we must detect the weak or forbidden absorptions in which the change in the Vibrational level is greater than 1 and these are known as overtones.