Solution

ID: past-exam-of-the-chemistry-course-of-the-year-3-of-the-natural-sciences-course-of-the-university-of-cambridge/2022/paper-2a/section-b/22/b/i/solution

Let . For a fixed row, moving one column to the right therefore gives
Thus adjacent-column entries decrease by the lower-state vibrational spacing, independent of the upper-state row in the ideal model. If the positive difference is instead defined as left minus right, it is . Stating the subtraction direction prevents an artificial negative vibrational frequency.

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